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I really enjoyed your discussion and rationale for a safety stop. As a diving medical physician, certified in Undersea & Hyperbaric Medicine, I can comfortably say that as far a "safety" which to me means avoiding bubble injury [bends and AGE] the position is of no relevance. The heart pumps in any orientation and off-gassing is a function of the circulation through the lungs. therefore, the position that the diver is most comfortable using is just fine, especially if that encourages always doing a safety stop. In diving, the "belts and suspenders" approach may well avoid many problems. Keep up the thought provoking videos. Thanks.
Ed, thank you so much for your comments. Couldn’t ask for a more qualified person to weigh in on this topic! Thanks for taking the time to add to this conversation!
I believe in this physician ,I'm sure he is spot on.everybody who says horizontal or vertical doesn't make a difference. What ever your comfortable doing is fine just as long as you do a safety stop.
Great topic to discuss. IMO…I have found in early instruction that the vertical v horizontal safety stop came down to the teaching decision of not only different instructors but also different teaching academies. Personally, I prefer vertical with my head at 5m with the rational, or irrational belief that gas rises easier vertically, however the theory or practicality pans out, position V or H does not outweigh the solid practice of always performing a safety stop. Great content guys. Looking forward to more…keeping the enjoyment of diving safe is the most important thing to remember and you guys always mention safety and fun. 🤿 Big thumbs up to all👍
I am a PADI and NAUI instructor with thousands of dives. A safety stop is not required, but, I would highly advise and always taught to do one. Especially if your workload down there is above normal. As for positioning when doing a safety stop I don't really have an opinion. I do them vertically or horizontally, whatever is comfortable to me at the time. I do try and concentrate on keeping my joints straight for good blood flow. Seems to me that bubbles want to rise so who knows...haha. I would rather you concentrate on practicing safe diving and HAVING FUN. Safe dives ladies and gents!! Try diving offshore in North Carolina, its pretty cool. Lots of wrecks and plenty of other stuff.
I prefer horizontal orientations in the water column generally because I find it easier to "maintain hover" in that position since the horizontal position presents more surface area to the direction of movement. However, if being visually aware of my surroundings is paramount, I will hold a vertical position. Summary? I use both depending on the need.
Regarding the comment you received ‘you should never be in a vertical position’. I’ve been surrounded by 4 oceanic white tips during a safety stop, trust me that’s not a situation where you want to be in perfect horizontal trim, rather presenting a larger profile in the water with the ability to spin on a dime, ie vertical. :-) Nice video gents.
Great to see you back!! Horizontal or vertical depends completely on the situation you are in. What I find more concerning is, that plenty of divers “shoot” up to the surface after the 3 minutes are over, and the DM/Guide signals to go up.
Great info. In a large group of divers, 30+, especially at a deep wreck, with a lot of beginner AOW divers trying to earn their AOW wreck and deep certifications, I will perform my Safety Stop in a horizontal hover on the mooring line below 20 ft or just above 15ft, to make room for all those students and divers at 15ft. It gets pretty crowded on the line. We have strong current in the Keys at the wrecks. So, a hand on the line is necessary.
Totally agree with you and let’s say that it’s also wrong to ascend rapidly to the surface from the safety stop. In the last 5 m there is a 0.5 ATM difference so, go slowly! 😊
I’m currently stationed in Germany. My wife and I were able to get PADI OW certified (all equipment included and zero additional fees occurred during/after the course) for 619 euros each. It was pretty pricey compared to the other (scarce) dive centers in our area. The class was basically private because we didn’t speak/understand a lot of German and we had an instructor (99%) to ourselves.
Welcome Back!! Missed these videos. As to a position for safety stops, I honestly think it comes down to diver's choice. As you demonstrated with the formulas, the difference in pressure is negligible. I personally do both given the situation, but mainly do a vertical one. I think the type of BCD also comes into play. Vest type BCD's tend to keep you vertical at the surface and wing style tend to keep you pushed forward a bit. Depending on what you're using, one position may be easier than the other. Not to say this shouldn't be controlled with buoyancy, but to keep a safety stop more relaxing I believe is important. If you're a very new diver, I don't believe you should be struggling and breathing heavily at the SS. Whatever makes it more relaxing at 15ft for you, as long as you can maintain it, I think should be just fine.
Great question guys. I've been diving since 1981 and have hovered both horizontally and vertically. And I questioned if I was off-gassing uniformly, but never dwelled on it. Thanks for doing the math.
Classy approach to comments. However, yall did the research and which is valuable. Thank you both for sharing your knowledge ! I will always do safety stop because its a good habit to have and to protect my sons. Thank you, great channel !!!
Never mind what hardheaded buddys who think their knowledge and ideas are far ahead and beyong those of others say. Great video and explanation. I always do my safety stop and ussually in vertical position but only because is more confortable.
Buoyancy control is key. Particularly for new divers a vertical ascent to 5@5 SS is often easiest. Left hand on LP Inflation/deflation hose, held above head - and computer in front of face to manage ascent rate & depth. If maintaining 5@5 is then easiest in a horizontal position, great. But often divers want to visually hold their position , within their dive group, by keeping face to face eye contact.
Very well presented. I do find it hard to understand that people might realise that safety stops are not compulsary for recreational diving, although as you say there can only be good from doing one if you can, but can also argue that doing one while vertical is somehow dangerous. I personally like to stay horizontal because it's a point in the dive where you are floating still and the lack of finning makes it obvious if there is something off with your trim. But I also like to be vertical for better visibility and SA when I'm putting up a DSMB and then heading for the surface. Great example also of the superiority of European units for doing these pressure sums in your head, much easier to divide by 10!
This is kind of like asking is it better to floss to before or after you brush. It doesn't matter just do it. Your BC and comfort level play a big part and if you can stay in the same position upright during your stop then why should it matter? With my wing I'm weighted to be horizontal but if I wear a jacket i like to chill in a kneeling position. You're going to move around a bit in any position even when holding a line.
thanks for the video, 99 times out of a hundred if I go deeper than 30 ft. I make a safety stop, 3 or 5 min at 15ish feet, I enjoy them especially if I'm on an anchor line or similar. can be tough in rough seas without something to hold on to. the thing about horizontal or vertical, it's up to the diver. the biggest issue I've seen is body temp. If you go down cold and come up warm, heating up to fast at the end of the dive vs. being cold at the end of the dive. DAN has a great video on this and explains the physiology behind it.
I find I like both. Especially with my pony. As we all know the al80 an my al19 provide pos buoyancy when low. I've also been workin on my personal bcd (lungs) to maintain depth. Yes horizontally you look cool but the purpose is safety not photo opp. I love the way yall give the data showing off gas rates and remind us how the science will affect us. We're all made different and need to concentrate more on depth and time then just looking good under water.
In life, I've learned to ask the experts and never pay attention to comments left for those experts. Those people that are always voicing their opinion and telling experts like you that you're wrong are losers that try to convince people how smart they are. Smart people don't have to try and convince other people of it, just like tough people never have to convince people they are. Ignore those fools.
Another note about safety stops: I have observed literally hundreds of divers that treat the end of their safety stop as a free pass to shoot to the surface or at least ascend too quickly. So many forget that this is the zone of largest volume changes of gases and should be taken slowly.
If you are a recreational diver that is staying within your no decompression limits, a safety stop is to be conservative and error on the side of caution (always a great idea in my opinion) not because it is required. So what difference does it really make vertical or horizontal?
All of a sudden we have hydrodynamics and physiology experts. Just do the safety stop at the depth vertical or horizontal. This is a recreational diver not some saturation trimix expedition
Great video, especially the calculations of pressure differentials on a vertical diver. My take: (and this ironically sounds contradictory), never believe in statements of absolutes. Yes, it makes sense to usually do something the same way in a given situation. But, then again, life is is mostly a situational game where you always should consider a plan B. A safety stop is a great opportunity to practice a horizontal hover, but if you’re not close enough to the bottom to stir up silt and you want simultaneous visibility of above and below, go vertical.
Yes, you guys are back! Looking forward to the rebreather video and the ANDP. As for this, I’ve done GUE and they are adamant about being horizontal but hey, for recreational diving it’s not that big a deal. If I were doing deco stops it’s another story but for diving on a reef to 40ft and hanging at 15ft for 3 minutes it’s not a big deal
Really good advice and also explanation on both types of safety stops I think some divers think they have learnt every thing to know about diving even as a diver my self I still read books on diving and also watch videos that u all post as I learn new things every time We must not think we know every thing Anyway thanks a lot for all the tips on diving keep posting All the best
Buoyancy is far more important than horizontal trim at a safety stop. If it’s easier to maintain your depth vertically, then do that. If it’s easier for you to maintain your depth horizontally, then do that. At least that’s my feeling on it. I will add, that being vertical, does allows you to look around easier, especially if boats are near.
Good to see you back guys! Great video. That 3 minute safety stop at the end of a dive is one of my happy places. Doesn't matter to me if I'm horizontal, vertical, or upside down (though I've never been upside down on a safety stop). What's more important to me (besides reflecting on the dive and just enjoying being where I am while gently floating up and down in the water column as I breathe), is my ascent from that safety stop depth. I love to rise and practice controlling my ascent as I exhale. I feel that the ascent rate from a safety is more critical than my position as I finish my wait. I've seen a lot of people go from safety stop depth to surface in no time, especially new divers. Any thoughts on that?
Come one, we are talking about a pressure difference of 0,1 bar if the divers length is 2 mtr. Sea water is 1 bar/10 mtr, so 0,1 bar/mtr. To me it is more important to be comfortable.
Fully endorse your comments about the desirability of a safety stop. I would go further if you have to surface without a stop because of lack of gas your dive planning and execution has failed. I bet divers would not be happy if a pilot did not keep a reserve and exhausted his fuel before landing! It should become normal practice to 1. Carry out a stop every dive (especially if you are doing repetitive dives and 2. Ensure you can maintain a consistent depth during the stop. SMP or shot lines can assist but should not be relied on, especially if a sea is running. So many times I have seen divers yo-yoing, dropping well below 5m and then even breaking the surface during their stop, or constantly finning to maintain depth. Use your stop to practice and perfect your buoyancy control - that will make you a more professional and safer diver.
Definitely shows good form and can be easier to maintain. However, I mostly spearfish, I tend to like being vertical because I’ve got my hands full with a gun and stringer of fish. Just seems comfortable to me.
I've once heard that an argument for the horizontal position - in diving in general, not just safety stops - is that puts less stress on the diver's heart, since the bloodflow doesn't fight against gravity that much. Is there any reason to that way of thinking? Also I definitely agree that being vertical in a drysuit is not a good time, especially at very low depths.
I know this is an old video - but I'd answer back with a question: "how much does your heart struggle while standing up?" if the answer is that it struggles a lot, should you even be snorkelling let alone diving?
My opinion is it doesn't matter if you're vertical or horizontal doing a safety stop. Where do these haters get their info that a diver needs to be horizontal while doing a safety stop?
Hi I think best way to make safety stop Moving or physically move let's make the muscles need oxygen So you release the nitrogen more faster Best regards
Great comment Mohmed! In a previous video where we discussed physical activities and DCS, we talked about the fact that divers who move around a bit and have limb movements showed less bubble formation in their blood stream post dive and it may be that they "off gas" more efficiently due to their movement! Thanks for watching!
If a safety stop can be completed at a range of depths, as long as it remains below a set number, I'm pretty sure the additional 2-4 feet either side by being upright is going to make little to no difference at all. I doubt there is much research on it but I'm willing to bet that there would be more of a difference (+/-) fropm how your circulatory system functions from horizontal to vertical than the margin created by not being 'all' at the same depth when linked to degassing rates. Personally, I think that the risk of hitting something/someone from slower rotations in a horizontal position whilst rising would (whilst tiny) present a greater risk than what viewers were concerned about. I tend to come up horizontally but that's likely due to wearing BPW making that much more comfortable.
Here's a definitive answer: it doesn't matter. I deco horizontally, just because it's comfortable to stay in that position for a long time. My tech instructors will switch it up depending on what's happening. Sometimes they'll stay vertical so that they have better visibility and awareness of what's going on. Awareness, comfort and safety are what matter, not your position. Additionally, recreational divers should always do a safety stop and should always have gas to do so. It's for safety. It's rarely _required_, but it's a great skill to practice, it adds to conservatism, etc. It's technical divers (or rec divers with understanding of GF, deco theory, knowledge of their SurfGF, etc) that may choose not to do a safety stop.
Hi guys. Great video, however, Lyle could you please elaborate on the statement why being horizontal is a better position "for a new diver"? That implies that an experienced diver should aim for vertical. Did you mean that? You demonstrate quite vividly why being vertical works in a diver's disadvantage, so why not just use the horizontal trim position the base platform?
Geir, I did not mean to imply that an experienced diver should aim for vertical positioning. What we were trying to emphasize is that being horizontal makes it EASIER for new divers because you are providing more surface area and drag to the water column. This makes buoyancy control somewhat easier for less experienced divers. As an experienced diver I think we have shown that being vertical or horizontal does not hugely affect their safety, but in a vertical position, you present less surface area to the water and therefore you have to more mindful of buoyancy control. Sorry if we confused you.
@@everythingscuba the statement seemed contradictory imho. You gave a very compelling argument for why one should aim stay in the prone position, illustrated by the falling piece of paper. But the same laws of physics apply to all divers, irrespective of experience level.
@@GeirAlstad I think the pros of the vertical position are situational. If I am doing a safety stop after a deep dive off a boat, I want to be able to keep an eye on the boat, the sub-surface buoy line and all the other divers- When vertical, I can spin around without effort to look at the boat or whatever. It's just more comfortable - and if there is no discernible difference in terms of safety, I don't see why not.
I'm in the safety stops are not mandatory, but are strongly advised, when possible I'll add a minute or two to the final deco stop for conservatism. 4:14 as soon as you've added those caveats I think you've shot all the rest of the arguments in the foot. If you took it from mandatory deco and then added a "This isn't mandatory so other factors eg comfort, the guide watching divers come into it. The math shows there very little pressure differential... so It's more important that you do the safety stop and slowly ascend at the end rather than blow the stop and/or popup at the end" One thing I'd add, the pose at 2:22, as graceful as it looks, shouldn't be encouraged because part of the reason for the stop is very gentle whole body exercise. With the legs and arms crossed the muscles aren't being used so will not off gas as quickly (yes this point comes back to mandatory deco)
A safety stop is better than none, so people can do what’s comfortable and easiest for them. The old school Buddha position is so outdated though. And technically it’s better to do in horizontal trim so your body parts are off gassing at the same depth and thus off gassing at the same rate
Agree with most of your comment except the “off gassing at the same rate”…….because of different tissue compartments none of us off gas at the same rate.
I do wonder if moderate movements might assist with off gassing from some area, assisting blood circulation mechanically especially around joints; also how increased breathing rate might influence same.
yes, it does. Not so much about the joints, but Flook 1997 "The effect of exercise on decompression bubbles" - faster gas in with more exercise at the bottom, and faster gas out with exercise at the top. The caveat is the strenuous exercise can increase the likelihood of big bubbles, so it seems you'd want to keep up a gentle level of activity, and the asleep/comatose motionless mid-water float wouldn't be the optimal. (and since safety stops aren't mandatory, just there for added off-gassing, you'd think that mild activity would be advocated for to further improve on things).
I personally do not believe that on a recreational dive, there is a significant difference in off gassing rates. perhaps on a deeper, longer or comercial type dive maybe, but not rec, diving.
I have a question. If diving without a safety stop within decompression limits. Will a leaner person with less body fat (lean like an athlete) be less likely to get the bends compared to a person with higher body fat (more on the obese side).
literature I've read isn't conclusive on that question specifically - "fatter" often functions as a stand in for "unfit", and fitness as well as pre--dive-exercise have been shown to be positives when it comes to bends. What I'm not 100% on is how much of that is because a fitter person will often go through less gas than an unfit person (so they've had less exposure to compressed gas) or how much is improved ability to off-gas. Simple answer, being fitter definitely seems to be much better, being leaner for a given respiratory rate isn't clear.
Don't do deep stops, it's that simple. You'll just be on-gassing more. Dozens or hundreds of videos with Simon Mitchell covering this topic if you're interested.
@@brois841 His videos are about deep deco on trimix, they have little relevance to recreational diving. Within recreational diving none of the slower compartments that he is talking about should have real inert gas load under that context. Now there is a doppler bubble study and found that divers that did a deep stop in addition to a deep stop had less bubbles that divers that just did a standard safety stop and even those that did an extended 5 minute safety stop. But this is a one off study that hasn't been repeated to test it across other profiles. So there is little data for recreational diving.
@@Teampegleg no way, Mitchell covers way more than those diving w/trimix and someone asking about stops may be curious about theory beyond recreational limits. Recreational divers don't plan, so it's common to wonder "what do I do if my computer is showing a minute deco stop?" When someone stays "within recreational diving" limits (depth and NDL), then by definition they shouldn't be overloading their slower compartments. The point still stands: zero reason to have a "deep stop" and the recommendation is to do a shallow (10-20ft) safety stop.
@@brois841 No, his data is specifically from data modeling and statistically analysis of super deep hypoxic trimix dives. And I haven't seen one yet that doesn't involve deep hypoxic trimix dives. And he is comparing super lower GFs like GUE standard of 20/85 vs his suggestion where the GF Low should be above 50%. Deep deco doesn't even become a factor until you are spending a ton of time at 330ft or more. Like the difference in deco at depth (100+ft) is a couple of minutes at most until your bottom depth gets below 300ft, and total run times are trivially similar if you are all running the same standard gases. And his idea of a deep stop is like 210ft for 5 minutes. And as I pointed out that actual doppler studies show within a recreational context adding a deep stop lower bubble counts more than shallow stops do alone. A one minute stop on back gas is a trivial amount of gas loading. It takes about 5 minutes of oxygen deco before you even get a stop below 10ft.
If you consider tissues ungassing rate, it is only fair to also consider, tissues never decompress at the same rate. That you learnin your DM Course and that decompression rate difference between tissues is already considered in all the diving computers algorithm, so you never go to a Deco dive for that reason.
Thanks for the video. A couple of comments - mostly around target audience. - anyone who doesn't know the pros and cons of vertical vs horizontal position during a safety stop probably doesn't know what an IDC instructor is. Or an MSDT instructor. I think scuba instructor is sufficient unless you are willing to at least hint why an IDC or MSDT instructor is more credible than a regular instructor. - One guy posits that a vertical position allows him to better track divers above and below - something he has to do when working as an instructor or dive master. Are instructors/dive masters your target audience for this video? Or are newer divers? If it is the latter, isn't the only diver for a newer diver to keep track of during the ascent their dive buddy? - The other guy offers "diving in areas where there is boat traffic" as another reason to have good visibility above your head at all times during the dive. Shouldn't the guidance to newer divers be - if you are diving in an area of boat traffic, you must ascend on the anchor line as your boat will serve as "shelter" from other boat traffic? And if ascending on the anchor line is not feasible for whatever reason, that deploying a surface marker buoy then becomes necessary to at least give oncoming boat traffic an indication that divers are ascending? On beach dives, isn't this why people tow a dive float?
Thanks for your opinions and thanks for watching. #1: Not sure what IDCS/MSDT has to do with target audience or diver knowledge about them. #2: What ifthe diver is diving with a group of 4 or 5 divers and not just one buddy? What if that group has variety of dive skill or experience so they each have their own buoyancy issues at SS….? #3: what if you are drift diving and there is no anchor line?……yes you’d put up a DSMB but does it matter if done in a vertical or horizontal position during SS? #4: we shore dive all the time in the USVI without a dive flag float. (Not required here). I’m guessing you are not our target audience but we appreciate you watching nonetheless!
@@everythingscuba #1 When I saw IDC and MSDT, the first question that popped into my head was, what do those acronyms mean and why is it relevant? I assume you post those titles to communicate credibility to your opinions. Assuming it is relatively new people who need the content you are providing, wouldn't it be helpful if they understood your type of instructor is more credible than a regular instructor? If that is not important/relevant, then why share that info? #2 Maybe just the way I was trained but the biggest groups of real buddies I have participated in is a group of 3. Even then, it is a challenge to keep everyone on the same page, particularly in low vis situations. In my experience, if you don't have a primary buddy, you have no buddy. On the cattle boats I have been on, even though a dive master is leading the dive, we paired up to have primary buddies. There are several reasons for this, not the least of which is when one diver is low on air, they ascend with a buddy. I know that in some places, they send up individual divers as each one gets low on gas. Again, an example of a group diving together but each diver not having a buddy. At any rate, this reason is completely different than talking about an instructor or a dive master who needs to keep track of others
There always has to be a critic in the crowd….🙄🙄🙄what caught me is not knowing what the terms IDC and MSDT mean………Sometimes it is just a good idea to pay attention to those that out rank you.
@@Randiosands Thanks for your reply. A few points: - Why do you think these people outrank anybody? They are scuba instructors. There is no rank associated with that. - Their video is talking about best practices for safety stops - specifically about vertical vs. horizontal orientation. This stuff basic information. Presumably their target audience are newer divers. As such, why are they assuming that the acronyms IDC or MSDT mean anything to their target audience? - Finally, I suppose you can characterize my comments as "critical". I would argue that my comments are constructive. They are intended to help the folks I am addressing do a better job and I offer specific ways they can do so. "Constructive criticism" is one of the best ways for all of us to get better. Now, you might not agree with my comments, that is fine. You are welcome to state why you think I am wrong.
@@adobo1970 I am not going to argue with you…..but you may want to check PADI ranking. There is 4 levels of instructors…..so yes, there is a ranking. Best wishes my friend
Nonsense. Do however you prefer. Sometimes I do safety stops vertically and sometimes horizontally. Been doing that for thirty five years. It just depends. Sometimes I prefer to see the surface and the boat.
Old hardhat pearl divers could only do their 'hang stop' ala safety stop in the vertical ... no problems. Why did they start doing the 'hang' ... they realised that 'prickles' in the back of the neck (mild bends) was far less! Vertical works.
I’ve been intrigued with some of the ISE Ratio Deco theories on decompression diving. They suggest having several standard depths to decompress at the end of the dive regardless of if it’s a dive performed within your NDL limit or not. Doing stops at 9/6/3 meters seems like it could be a similar argument to the difference tissue compartment off gassing in the vertical orientation. I am not professionally trained to dive beyond my NDL, but I feel like most of us rec divers seem to forget or were not taught that every dive (rec or tec) is a decompression dive. This means a safety stop or a decompression stop is doing the same thing for us no matter what we call it. My personal practice is to do a 3 minute safety stop at 6 meters/18 feet. I just recently learned of a fellow diver I know who has thousands of tec dives get bent while following all decompression plans and diving a conservative plan. DAN evaluated his dove profile and told him it was an undeserved hit. It’s never a guarantee we won’t get bent. That’s caused me to consider stretching my safety stops to 5 minutes if I have the air. I’ve got Deco for Divers book in the mail right now, so I’m excited to learn more about it.
Why on earth do a vertical safetystop? If bad trim is an excuse, work on the trim. If there’s boat traffic, bring a smb. Lots of people? Keep a better buddy position;) Nice video as always gentlemen. // cold snowy regards from Sweden
On deep dives there's not much to look at when horizontal. You can't see the boat and the other divers at the same time. Vertical is more comfortable and gives you increased situational awareness.
@@joakimdiver1120 I'm curious: What is my smb going to do? It's my boat parked at the sub surface buoy. ( edit: I dive mostly in low population equatorial regions on old wrecks at the recreational limit. I realize diving experiences are very different in other parts of the world. I will get around to all of them- someday).
@@joakimdiver1120 in some conditions it improves situational awareness/visibility and thus safety. You don't have to crank your neck to see your buddies and your computer at the same time. If my buddies are decoing slightly above me I'll take a more vertical stance. If they're next to/below me I'll stay horizontal. When you're in the middle of the ocean safety is #1, not your body position. Obviously my answer comes from a technical diving mindset. If you're recreational then a safety stop is a great time to practice buoyancy/trim. I always encourage people to stay horizontal for that reason, but it's not a rule. It's especially harder for rec divers who aren't using BP/W, for example.
There are plenty of areas in this world, where fishermen and recreational boats don´t give a flying "F" about your SMB and you want to have the surface and your divers in a 360-view while staying vertical.
Hi Josh, hi Lyell, I'm so happy you did the math, but you should have looked up some reference values. 0.1bar, or 1.47PSIG are not negligible. If you check out NOAAs level of concern for blast waves: response.restoration.noaa.gov/oil-and-chemical-spills/chemical-spills/resources/overpressure-levels-concern.html then you will find a table Overpressure(psig) Expected Damage 0.04 Loud noise (143 db); sonic boom glass failure. 0.15 Typical pressure for glass failure. 0.40 Limited minor structural damage. 0.50-1.0 Windows usually shattered; some window frame damage. 0.70 Minor damage to house structures. 1.0 Partial demolition of houses; made uninhabitable. Please, show me how you can blow harder than 1.47PSIG. But frankly, I understand that there is a lot to do with the rapid changes of pressure, so lets talk about your ability to overcome this pressure in a more scuba related way. Can you go 3ft underwater and snorkel? I seriously doubt it. The general maximum length a snorkel can be and a fit human will still be able to inflate their lungs against the water pressure is 2ft. We're talking about going 50% deeper than what is humanly possible here. How can we know this? Well, there is this paper here that cites another paper behind a paywall I'm afraid www.ncbi.nlm.nih.gov/books/NBK559293/ but the citation in this paper gives us the info we need. "Transpulmonary pressures of more than 60 to 70 mmHg can cause an alveolar rupture." 60 to 70 mmHg is 1.16 to 1.35 PSIG. Your 1.47PSIG blow would cause your alveoli to rupture. The pressure difference we are talking about here is more than enough to get a massive lung barotrauma if you were holding a full lung of breath and ascended that much.
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I really enjoyed your discussion and rationale for a safety stop. As a diving medical physician, certified in Undersea & Hyperbaric Medicine, I can comfortably say that as far a "safety" which to me means avoiding bubble injury [bends and AGE] the position is of no relevance. The heart pumps in any orientation and off-gassing is a function of the circulation through the lungs. therefore, the position that the diver is most comfortable using is just fine, especially if that encourages always doing a safety stop. In diving, the "belts and suspenders" approach may well avoid many problems. Keep up the thought provoking videos. Thanks.
Ed, thank you so much for your comments. Couldn’t ask for a more qualified person to weigh in on this topic! Thanks for taking the time to add to this conversation!
I believe in this physician ,I'm sure he is spot on.everybody who says horizontal or vertical doesn't make a difference. What ever your comfortable doing is fine just as long as you do a safety stop.
Great topic to discuss. IMO…I have found in early instruction that the vertical v horizontal safety stop came down to the teaching decision of not only different instructors but also different teaching academies. Personally, I prefer vertical with my head at 5m with the rational, or irrational belief that gas rises easier vertically, however the theory or practicality pans out, position V or H does not outweigh the solid practice of always performing a safety stop. Great content guys. Looking forward to more…keeping the enjoyment of diving safe is the most important thing to remember and you guys always mention safety and fun. 🤿 Big thumbs up to all👍
I am a PADI and NAUI instructor with thousands of dives. A safety stop is not required, but, I would highly advise and always taught to do one. Especially if your workload down there is above normal. As for positioning when doing a safety stop I don't really have an opinion. I do them vertically or horizontally, whatever is comfortable to me at the time. I do try and concentrate on keeping my joints straight for good blood flow. Seems to me that bubbles want to rise so who knows...haha. I would rather you concentrate on practicing safe diving and HAVING FUN. Safe dives ladies and gents!! Try diving offshore in North Carolina, its pretty cool. Lots of wrecks and plenty of other stuff.
I prefer horizontal orientations in the water column generally because I find it easier to "maintain hover" in that position since the horizontal position presents more surface area to the direction of movement. However, if being visually aware of my surroundings is paramount, I will hold a vertical position. Summary? I use both depending on the need.
Regarding the comment you received ‘you should never be in a vertical position’. I’ve been surrounded by 4 oceanic white tips during a safety stop, trust me that’s not a situation where you want to be in perfect horizontal trim, rather presenting a larger profile in the water with the ability to spin on a dime, ie vertical. :-) Nice video gents.
Do you have a separate BCD for those large balls ?
@@sarahann530 hahahahaha! Great reply that!
Great to see you back!!
Horizontal or vertical depends completely on the situation you are in.
What I find more concerning is, that plenty of divers “shoot” up to the surface after the 3 minutes are over, and the DM/Guide signals to go up.
Great info. In a large group of divers, 30+, especially at a deep wreck, with a lot of beginner AOW divers trying to earn their AOW wreck and deep certifications, I will perform my Safety Stop in a horizontal hover on the mooring line below 20 ft or just above 15ft, to make room for all those students and divers at 15ft. It gets pretty crowded on the line. We have strong current in the Keys at the wrecks. So, a hand on the line is necessary.
Totally agree with you and let’s say that it’s also wrong to ascend rapidly to the surface from the safety stop. In the last 5 m there is a 0.5 ATM difference so, go slowly! 😊
I’m currently stationed in Germany. My wife and I were able to get PADI OW certified (all equipment included and zero additional fees occurred during/after the course) for 619 euros each. It was pretty pricey compared to the other (scarce) dive centers in our area. The class was basically private because we didn’t speak/understand a lot of German and we had an instructor (99%) to ourselves.
Welcome Back!! Missed these videos. As to a position for safety stops, I honestly think it comes down to diver's choice. As you demonstrated with the formulas, the difference in pressure is negligible. I personally do both given the situation, but mainly do a vertical one. I think the type of BCD also comes into play. Vest type BCD's tend to keep you vertical at the surface and wing style tend to keep you pushed forward a bit. Depending on what you're using, one position may be easier than the other. Not to say this shouldn't be controlled with buoyancy, but to keep a safety stop more relaxing I believe is important. If you're a very new diver, I don't believe you should be struggling and breathing heavily at the SS. Whatever makes it more relaxing at 15ft for you, as long as you can maintain it, I think should be just fine.
That’s why I always safety stop at a 45 degree angle.
Great question guys. I've been diving since 1981 and have hovered both horizontally and vertically. And I questioned if I was off-gassing uniformly, but never dwelled on it. Thanks for doing the math.
Classy approach to comments. However, yall did the research and which is valuable. Thank you both for sharing your knowledge ! I will always do safety stop because its a good habit to have and to protect my sons. Thank you, great channel !!!
Never mind what hardheaded buddys who think their knowledge and ideas are far ahead and beyong those of others say.
Great video and explanation. I always do my safety stop and ussually in vertical position but only because is more confortable.
Buoyancy control is key. Particularly for new divers a vertical ascent to 5@5 SS is often easiest. Left hand on LP Inflation/deflation hose, held above head - and computer in front of face to manage ascent rate & depth. If maintaining 5@5 is then easiest in a horizontal position, great. But often divers want to visually hold their position , within their dive group, by keeping face to face eye contact.
Very well presented. I do find it hard to understand that people might realise that safety stops are not compulsary for recreational diving, although as you say there can only be good from doing one if you can, but can also argue that doing one while vertical is somehow dangerous. I personally like to stay horizontal because it's a point in the dive where you are floating still and the lack of finning makes it obvious if there is something off with your trim. But I also like to be vertical for better visibility and SA when I'm putting up a DSMB and then heading for the surface.
Great example also of the superiority of European units for doing these pressure sums in your head, much easier to divide by 10!
Should be doing the safety stop. Just be happy people do it
This is kind of like asking is it better to floss to before or after you brush. It doesn't matter just do it. Your BC and comfort level play a big part and if you can stay in the same position upright during your stop then why should it matter? With my wing I'm weighted to be horizontal but if I wear a jacket i like to chill in a kneeling position. You're going to move around a bit in any position even when holding a line.
That's an epic picture of the vertical pose. I'm definitely going to get that shot of my son and myself. I agree that it's a negligible difference.
Welcome back Lyell & Josh. A nice systematic approach to a somewhat controversial topic.
thanks for the video, 99 times out of a hundred if I go deeper than 30 ft. I make a safety stop, 3 or 5 min at 15ish feet, I enjoy them especially if I'm on an anchor line or similar. can be tough in rough seas without something to hold on to. the thing about horizontal or vertical, it's up to the diver. the biggest issue I've seen is body temp. If you go down cold and come up warm, heating up to fast at the end of the dive vs. being cold at the end of the dive. DAN has a great video on this and explains the physiology behind it.
Would love to have you share a link to this DAN video. Thanks William!
I find I like both. Especially with my pony. As we all know the al80 an my al19 provide pos buoyancy when low. I've also been workin on my personal bcd (lungs) to maintain depth. Yes horizontally you look cool but the purpose is safety not photo opp. I love the way yall give the data showing off gas rates and remind us how the science will affect us. We're all made different and need to concentrate more on depth and time then just looking good under water.
Great to have you guys back. Honestly I was a bit concerned for a while giving your little incident in Sorroco. Look forward to future content!
Thanks John. Our hiatus was not related to health problems. We super glad to be back though. :)
In life, I've learned to ask the experts and never pay attention to comments left for those experts. Those people that are always voicing their opinion and telling experts like you that you're wrong are losers that try to convince people how smart they are. Smart people don't have to try and convince other people of it, just like tough people never have to convince people they are.
Ignore those fools.
Loved how you explained the tissue compartments and all that would love learn more about that if you guys ever wanted to do that!
Another note about safety stops: I have observed literally hundreds of divers that treat the end of their safety stop as a free pass to shoot to the surface or at least ascend too quickly. So many forget that this is the zone of largest volume changes of gases and should be taken slowly.
+Patrick Wissing great point. That is something we tried to emphasize in our initial video on how to perform a safety stop. Thanks for watching
If you are a recreational diver that is staying within your no decompression limits, a safety stop is to be conservative and error on the side of caution (always a great idea in my opinion) not because it is required. So what difference does it really make vertical or horizontal?
All of a sudden we have hydrodynamics and physiology experts. Just do the safety stop at the depth vertical or horizontal. This is a recreational diver not some saturation trimix expedition
And if your buddy pass out or something.. how fast can you go to you buddy if you are vertical?
Great video, especially the calculations of pressure differentials on a vertical diver. My take: (and this ironically sounds contradictory), never believe in statements of absolutes. Yes, it makes sense to usually do something the same way in a given situation. But, then again, life is is mostly a situational game where you always should consider a plan B. A safety stop is a great opportunity to practice a horizontal hover, but if you’re not close enough to the bottom to stir up silt and you want simultaneous visibility of above and below, go vertical.
Yes, you guys are back! Looking forward to the rebreather video and the ANDP. As for this, I’ve done GUE and they are adamant about being horizontal but hey, for recreational diving it’s not that big a deal. If I were doing deco stops it’s another story but for diving on a reef to 40ft and hanging at 15ft for 3 minutes it’s not a big deal
Yay, so glad you guys are back! Missed your videos, and looking forward to more of you!
Really good advice and also explanation on both types of safety stops
I think some divers think they have learnt every thing to know about diving even as a diver my self I still read books on diving and also watch videos that u all post as I learn new things every time
We must not think we know every thing
Anyway thanks a lot for all the tips on diving keep posting
All the best
+DiDives thank you for your kind words and thank you for watching our channel!
Glad to see you guys again! Well done and bravo!
Buoyancy is far more important than horizontal trim at a safety stop. If it’s easier to maintain your depth vertically, then do that. If it’s easier for you to maintain your depth horizontally, then do that. At least that’s my feeling on it. I will add, that being vertical, does allows you to look around easier, especially if boats are near.
And if your buddy pass out? How fast can you swim to him if you are in a vertical position?
Great topic with plenty of basic facts explained.
Very helpful and presented in a articulate and professional manner. Great job guys. 👍
Great work guys, love your channel
It’s better to look bigger by standing up in the water especially if there is a chance of sharks in the area .. more defensive position for sure ..
Thanks guys, nice consideration and analysis.
Good to see you back guys! Great video. That 3 minute safety stop at the end of a dive is one of my happy places. Doesn't matter to me if I'm horizontal, vertical, or upside down (though I've never been upside down on a safety stop). What's more important to me (besides reflecting on the dive and just enjoying being where I am while gently floating up and down in the water column as I breathe), is my ascent from that safety stop depth. I love to rise and practice controlling my ascent as I exhale. I feel that the ascent rate from a safety is more critical than my position as I finish my wait. I've seen a lot of people go from safety stop depth to surface in no time, especially new divers. Any thoughts on that?
Great video, very informative
Come one, we are talking about a pressure difference of 0,1 bar if the divers length is 2 mtr. Sea water is 1 bar/10 mtr, so 0,1 bar/mtr. To me it is more important to be comfortable.
Fully endorse your comments about the desirability of a safety stop. I would go further if you have to surface without a stop because of lack of gas your dive planning and execution has failed. I bet divers would not be happy if a pilot did not keep a reserve and exhausted his fuel before landing! It should become normal practice to 1. Carry out a stop every dive (especially if you are doing repetitive dives and 2. Ensure you can maintain a consistent depth during the stop. SMP or shot lines can assist but should not be relied on, especially if a sea is running. So many times I have seen divers yo-yoing, dropping well below 5m and then even breaking the surface during their stop, or constantly finning to maintain depth. Use your stop to practice and perfect your buoyancy control - that will make you a more professional and safer diver.
Welcome back guys
Horizontal is ideal. However there is not a hard and fast right answer. It is situational.
I believe some would suggest horizontal is better because it shows a better control of your buoyancy.
I agree physics doesn’t show a clear advantage
Couldn't agree more Pablo. It definitely shows good diving form and buoyancy control is easier when horizontal. Thanks for watching!
Definitely shows good form and can be easier to maintain. However, I mostly spearfish, I tend to like being vertical because I’ve got my hands full with a gun and stringer of fish. Just seems comfortable to me.
I've once heard that an argument for the horizontal position - in diving in general, not just safety stops - is that puts less stress on the diver's heart, since the bloodflow doesn't fight against gravity that much. Is there any reason to that way of thinking?
Also I definitely agree that being vertical in a drysuit is not a good time, especially at very low depths.
I know this is an old video - but I'd answer back with a question: "how much does your heart struggle while standing up?" if the answer is that it struggles a lot, should you even be snorkelling let alone diving?
Just do in any position you want as long as you do it. It is better than none. You can do upside down if you like.
My opinion is it doesn't matter if you're vertical or horizontal doing a safety stop. Where do these haters get their info that a diver needs to be horizontal while doing a safety stop?
Hi
I think best way to make safety stop
Moving or physically move let's make the muscles need oxygen
So you release the nitrogen more faster
Best regards
Great comment Mohmed! In a previous video where we discussed physical activities and DCS, we talked about the fact that divers who move around a bit and have limb movements showed less bubble formation in their blood stream post dive and it may be that they "off gas" more efficiently due to their movement! Thanks for watching!
Very well explained 👌🏽
If a safety stop can be completed at a range of depths, as long as it remains below a set number, I'm pretty sure the additional 2-4 feet either side by being upright is going to make little to no difference at all. I doubt there is much research on it but I'm willing to bet that there would be more of a difference (+/-) fropm how your circulatory system functions from horizontal to vertical than the margin created by not being 'all' at the same depth when linked to degassing rates.
Personally, I think that the risk of hitting something/someone from slower rotations in a horizontal position whilst rising would (whilst tiny) present a greater risk than what viewers were concerned about. I tend to come up horizontally but that's likely due to wearing BPW making that much more comfortable.
Here's a definitive answer: it doesn't matter. I deco horizontally, just because it's comfortable to stay in that position for a long time. My tech instructors will switch it up depending on what's happening. Sometimes they'll stay vertical so that they have better visibility and awareness of what's going on. Awareness, comfort and safety are what matter, not your position. Additionally, recreational divers should always do a safety stop and should always have gas to do so. It's for safety. It's rarely _required_, but it's a great skill to practice, it adds to conservatism, etc. It's technical divers (or rec divers with understanding of GF, deco theory, knowledge of their SurfGF, etc) that may choose not to do a safety stop.
Thanks for you insightful comments! Appreciated! Thanks for watching!
Hi guys. Great video, however, Lyle could you please elaborate on the statement why being horizontal is a better position "for a new diver"? That implies that an experienced diver should aim for vertical. Did you mean that? You demonstrate quite vividly why being vertical works in a diver's disadvantage, so why not just use the horizontal trim position the base platform?
Geir, I did not mean to imply that an experienced diver should aim for vertical positioning. What we were trying to emphasize is that being horizontal makes it EASIER for new divers because you are providing more surface area and drag to the water column. This makes buoyancy control somewhat easier for less experienced divers. As an experienced diver I think we have shown that being vertical or horizontal does not hugely affect their safety, but in a vertical position, you present less surface area to the water and therefore you have to more mindful of buoyancy control. Sorry if we confused you.
@@everythingscuba the statement seemed contradictory imho. You gave a very compelling argument for why one should aim stay in the prone position, illustrated by the falling piece of paper. But the same laws of physics apply to all divers, irrespective of experience level.
@@GeirAlstad I think the pros of the vertical position are situational. If I am doing a safety stop after a deep dive off a boat, I want to be able to keep an eye on the boat, the sub-surface buoy line and all the other divers- When vertical, I can spin around without effort to look at the boat or whatever. It's just more comfortable - and if there is no discernible difference in terms of safety, I don't see why not.
Why does Josh use air quotes every time he says "off-gassing?" 🤔
I'm in the safety stops are not mandatory, but are strongly advised, when possible I'll add a minute or two to the final deco stop for conservatism.
4:14 as soon as you've added those caveats I think you've shot all the rest of the arguments in the foot. If you took it from mandatory deco and then added a "This isn't mandatory so other factors eg comfort, the guide watching divers come into it. The math shows there very little pressure differential... so It's more important that you do the safety stop and slowly ascend at the end rather than blow the stop and/or popup at the end"
One thing I'd add, the pose at 2:22, as graceful as it looks, shouldn't be encouraged because part of the reason for the stop is very gentle whole body exercise. With the legs and arms crossed the muscles aren't being used so will not off gas as quickly (yes this point comes back to mandatory deco)
Thanks for your comments Tim and thanks for watching!
A safety stop is better than none, so people can do what’s comfortable and easiest for them. The old school Buddha position is so outdated though. And technically it’s better to do in horizontal trim so your body parts are off gassing at the same depth and thus off gassing at the same rate
Agree with most of your comment except the “off gassing at the same rate”…….because of different tissue compartments none of us off gas at the same rate.
I do wonder if moderate movements might assist with off gassing from some area, assisting blood circulation mechanically especially around joints; also how increased breathing rate might influence same.
yes, it does. Not so much about the joints, but Flook 1997 "The effect of exercise on decompression bubbles" - faster gas in with more exercise at the bottom, and faster gas out with exercise at the top. The caveat is the strenuous exercise can increase the likelihood of big bubbles, so it seems you'd want to keep up a gentle level of activity, and the asleep/comatose motionless mid-water float wouldn't be the optimal. (and since safety stops aren't mandatory, just there for added off-gassing, you'd think that mild activity would be advocated for to further improve on things).
@@quickdry3 good info, thx..
I was taught to always do a safety stop. I was told the clue is in the title. SAFETY STOP
I personally do not believe that on a recreational dive, there is a significant difference in off gassing rates. perhaps on a deeper, longer or comercial type dive maybe, but not rec, diving.
What does this have to do with the extra string i cut off my new reel?
Anything wrong with horizontal but upside down? Facing surface?
Jacques is with an s, Jacques Cousteau
I have a question. If diving without a safety stop within decompression limits. Will a leaner person with less body fat (lean like an athlete) be less likely to get the bends compared to a person with higher body fat (more on the obese side).
literature I've read isn't conclusive on that question specifically - "fatter" often functions as a stand in for "unfit", and fitness as well as pre--dive-exercise have been shown to be positives when it comes to bends. What I'm not 100% on is how much of that is because a fitter person will often go through less gas than an unfit person (so they've had less exposure to compressed gas) or how much is improved ability to off-gas. Simple answer, being fitter definitely seems to be much better, being leaner for a given respiratory rate isn't clear.
Could you discuss the pros and cons of deep stops in addition to the usual safety stop in recreational diving?
Don't do deep stops, it's that simple. You'll just be on-gassing more. Dozens or hundreds of videos with Simon Mitchell covering this topic if you're interested.
@@brois841 Thank you!!
@@brois841 His videos are about deep deco on trimix, they have little relevance to recreational diving. Within recreational diving none of the slower compartments that he is talking about should have real inert gas load under that context.
Now there is a doppler bubble study and found that divers that did a deep stop in addition to a deep stop had less bubbles that divers that just did a standard safety stop and even those that did an extended 5 minute safety stop. But this is a one off study that hasn't been repeated to test it across other profiles. So there is little data for recreational diving.
@@Teampegleg no way, Mitchell covers way more than those diving w/trimix and someone asking about stops may be curious about theory beyond recreational limits. Recreational divers don't plan, so it's common to wonder "what do I do if my computer is showing a minute deco stop?"
When someone stays "within recreational diving" limits (depth and NDL), then by definition they shouldn't be overloading their slower compartments.
The point still stands: zero reason to have a "deep stop" and the recommendation is to do a shallow (10-20ft) safety stop.
@@brois841 No, his data is specifically from data modeling and statistically analysis of super deep hypoxic trimix dives. And I haven't seen one yet that doesn't involve deep hypoxic trimix dives. And he is comparing super lower GFs like GUE standard of 20/85 vs his suggestion where the GF Low should be above 50%. Deep deco doesn't even become a factor until you are spending a ton of time at 330ft or more. Like the difference in deco at depth (100+ft) is a couple of minutes at most until your bottom depth gets below 300ft, and total run times are trivially similar if you are all running the same standard gases. And his idea of a deep stop is like 210ft for 5 minutes.
And as I pointed out that actual doppler studies show within a recreational context adding a deep stop lower bubble counts more than shallow stops do alone.
A one minute stop on back gas is a trivial amount of gas loading. It takes about 5 minutes of oxygen deco before you even get a stop below 10ft.
I do my safety stop in a vertical position.
If you consider tissues ungassing rate, it is only fair to also consider, tissues never decompress at the same rate. That you learnin your DM Course and that decompression rate difference between tissues is already considered in all the diving computers algorithm, so you never go to a Deco dive for that reason.
Thanks for the video. A couple of comments - mostly around target audience.
- anyone who doesn't know the pros and cons of vertical vs horizontal position during a safety stop probably doesn't know what an IDC instructor is. Or an MSDT instructor. I think scuba instructor is sufficient unless you are willing to at least hint why an IDC or MSDT instructor is more credible than a regular instructor.
- One guy posits that a vertical position allows him to better track divers above and below - something he has to do when working as an instructor or dive master. Are instructors/dive masters your target audience for this video? Or are newer divers? If it is the latter, isn't the only diver for a newer diver to keep track of during the ascent their dive buddy?
- The other guy offers "diving in areas where there is boat traffic" as another reason to have good visibility above your head at all times during the dive. Shouldn't the guidance to newer divers be - if you are diving in an area of boat traffic, you must ascend on the anchor line as your boat will serve as "shelter" from other boat traffic? And if ascending on the anchor line is not feasible for whatever reason, that deploying a surface marker buoy then becomes necessary to at least give oncoming boat traffic an indication that divers are ascending? On beach dives, isn't this why people tow a dive float?
Thanks for your opinions and thanks for watching.
#1: Not sure what IDCS/MSDT has to do with target audience or diver knowledge about them.
#2: What ifthe diver is diving with a group of 4 or 5 divers and not just one buddy? What if that group has variety of dive skill or experience so they each have their own buoyancy issues at SS….?
#3: what if you are drift diving and there is no anchor line?……yes you’d put up a DSMB but does it matter if done in a vertical or horizontal position during SS?
#4: we shore dive all the time in the USVI without a dive flag float. (Not required here).
I’m guessing you are not our target audience but we appreciate you watching nonetheless!
@@everythingscuba
#1 When I saw IDC and MSDT, the first question that popped into my head was, what do those acronyms mean and why is it relevant? I assume you post those titles to communicate credibility to your opinions. Assuming it is relatively new people who need the content you are providing, wouldn't it be helpful if they understood your type of instructor is more credible than a regular instructor? If that is not important/relevant, then why share that info?
#2 Maybe just the way I was trained but the biggest groups of real buddies I have participated in is a group of 3. Even then, it is a challenge to keep everyone on the same page, particularly in low vis situations. In my experience, if you don't have a primary buddy, you have no buddy. On the cattle boats I have been on, even though a dive master is leading the dive, we paired up to have primary buddies. There are several reasons for this, not the least of which is when one diver is low on air, they ascend with a buddy. I know that in some places, they send up individual divers as each one gets low on gas. Again, an example of a group diving together but each diver not having a buddy. At any rate, this reason is completely different than talking about an instructor or a dive master who needs to keep track of others
There always has to be a critic in the crowd….🙄🙄🙄what caught me is not knowing what the terms IDC and MSDT mean………Sometimes it is just a good idea to pay attention to those that out rank you.
@@Randiosands Thanks for your reply. A few points:
- Why do you think these people outrank anybody? They are scuba instructors. There is no rank associated with that.
- Their video is talking about best practices for safety stops - specifically about vertical vs. horizontal orientation. This stuff basic information. Presumably their target audience are newer divers. As such, why are they assuming that the acronyms IDC or MSDT mean anything to their target audience?
- Finally, I suppose you can characterize my comments as "critical". I would argue that my comments are constructive. They are intended to help the folks I am addressing do a better job and I offer specific ways they can do so. "Constructive criticism" is one of the best ways for all of us to get better. Now, you might not agree with my comments, that is fine. You are welcome to state why you think I am wrong.
@@adobo1970 I am not going to argue with you…..but you may want to check PADI ranking. There is 4 levels of instructors…..so yes, there is a ranking. Best wishes my friend
Nonsense. Do however you prefer. Sometimes I do safety stops vertically and sometimes horizontally. Been doing that for thirty five years. It just depends. Sometimes I prefer to see the surface and the boat.
Old hardhat pearl divers could only do their 'hang stop' ala safety stop in the vertical ... no problems. Why did they start doing the 'hang' ... they realised that 'prickles' in the back of the neck (mild bends) was far less! Vertical works.
I’ve been intrigued with some of the ISE Ratio Deco theories on decompression diving. They suggest having several standard depths to decompress at the end of the dive regardless of if it’s a dive performed within your NDL limit or not. Doing stops at 9/6/3 meters seems like it could be a similar argument to the difference tissue compartment off gassing in the vertical orientation. I am not professionally trained to dive beyond my NDL, but I feel like most of us rec divers seem to forget or were not taught that every dive (rec or tec) is a decompression dive. This means a safety stop or a decompression stop is doing the same thing for us no matter what we call it. My personal practice is to do a 3 minute safety stop at 6 meters/18 feet. I just recently learned of a fellow diver I know who has thousands of tec dives get bent while following all decompression plans and diving a conservative plan. DAN evaluated his dove profile and told him it was an undeserved hit. It’s never a guarantee we won’t get bent. That’s caused me to consider stretching my safety stops to 5 minutes if I have the air. I’ve got Deco for Divers book in the mail right now, so I’m excited to learn more about it.
Why on earth do a vertical safetystop? If bad trim is an excuse, work on the trim. If there’s boat traffic, bring a smb. Lots of people? Keep a better buddy position;) Nice video as always gentlemen. // cold snowy regards from Sweden
On deep dives there's not much to look at when horizontal. You can't see the boat and the other divers at the same time. Vertical is more comfortable and gives you increased situational awareness.
@@chrisrunch7348 Bring a smb- boat problem solved;)
@@joakimdiver1120 I'm curious: What is my smb going to do? It's my boat parked at the sub surface buoy. ( edit: I dive mostly in low population equatorial regions on old wrecks at the recreational limit. I realize diving experiences are very different in other parts of the world. I will get around to all of them- someday).
@@joakimdiver1120 in some conditions it improves situational awareness/visibility and thus safety. You don't have to crank your neck to see your buddies and your computer at the same time. If my buddies are decoing slightly above me I'll take a more vertical stance. If they're next to/below me I'll stay horizontal. When you're in the middle of the ocean safety is #1, not your body position.
Obviously my answer comes from a technical diving mindset. If you're recreational then a safety stop is a great time to practice buoyancy/trim. I always encourage people to stay horizontal for that reason, but it's not a rule. It's especially harder for rec divers who aren't using BP/W, for example.
There are plenty of areas in this world, where fishermen and recreational boats don´t give a flying "F" about your SMB and you want to have the surface and your divers in a 360-view while staying vertical.
Hi Josh, hi Lyell, I'm so happy you did the math, but you should have looked up some reference values. 0.1bar, or 1.47PSIG are not negligible. If you check out NOAAs level of concern for blast waves: response.restoration.noaa.gov/oil-and-chemical-spills/chemical-spills/resources/overpressure-levels-concern.html then you will find a table
Overpressure(psig) Expected Damage
0.04 Loud noise (143 db); sonic boom glass failure.
0.15 Typical pressure for glass failure.
0.40 Limited minor structural damage.
0.50-1.0 Windows usually shattered; some window frame damage.
0.70 Minor damage to house structures.
1.0 Partial demolition of houses; made uninhabitable.
Please, show me how you can blow harder than 1.47PSIG.
But frankly, I understand that there is a lot to do with the rapid changes of pressure, so lets talk about your ability to overcome this pressure in a more scuba related way. Can you go 3ft underwater and snorkel? I seriously doubt it. The general maximum length a snorkel can be and a fit human will still be able to inflate their lungs against the water pressure is 2ft. We're talking about going 50% deeper than what is humanly possible here. How can we know this? Well, there is this paper here that cites another paper behind a paywall I'm afraid
www.ncbi.nlm.nih.gov/books/NBK559293/
but the citation in this paper gives us the info we need.
"Transpulmonary pressures of more than 60 to 70 mmHg can cause an alveolar rupture."
60 to 70 mmHg is 1.16 to 1.35 PSIG. Your 1.47PSIG blow would cause your alveoli to rupture. The pressure difference we are talking about here is more than enough to get a massive lung barotrauma if you were holding a full lung of breath and ascended that much.
Tobias, as always thank you for your always excellent analysis! This is why we love having our viewers like you share their ideas or additional information! Very much appreciated!