Welp… we had a close call while diving and I was looking for some input. Me and a buddy both have about 115 dives each, dove at the same lake we normally drysuit dive in, did the same dive we have done probably 60 times or more, and thank God, we made it out okay. So here is the story. On a previous dive a week earlier, we found a new rock structure at about 110 feet of depth and about 220-250 yards from the shore we enter at. We dove it on air, and everything went just fine a week earlier. The day of the close call, the temperature outside was a hot and muggy 85 degrees at about 10am on the surface, so we readied our gear right at the entry point to minimize the amount of time we would be out of the water in full gear. Wearing a triple layered fleece undergarment under the drysuit, things get hot very fast. We both got in the waist deep water and it took maybe 3-minutes longer to get in the water than normal, as we found a small leak on my buddy’s inflater button, but it was not bad enough to call the dive. We always dive with a spare 20 cuft pony bottles for added safety, as visibility can be pretty bad sometimes. This dive, we planned ahead, and dove with 100 cuft, 30% NITROX (outlier 1). Once we were in the water, I set the dive flag and we began our descent. At around 80 feet I felt like I was having difficulty going as fast as my dive buddy (outlier 2) and signaled for him to slow down, as we needed to follow our compass heading and stay together to find the new rock formation. Normally the roles are reversed and I am much faster than my dive buddy, but this dive was the first time where the roles were reversed. That’s why I am calling it an outlier.
At about 100 feet, we got side-by-side and continued down to about 120 feet, where the terrain levels off, and we were set for about a 7-minute swim to the rock structure. At about 2-minutes into being at 120 feet (6-minutes into the dive), I began to feel narced. I’ve been narced plenty of times so I didn’t really think anything of it, but at almost that exact moment of I felt narced, I hear my dive buddy start making moaning / labored breathing noises in his regulator. Seconds later, I began to feel more narced than I have ever been, and begin to hear my subconscious telling me, “you can’t be at this depth… something is wrong… is this gas fucked?... you need to surface”. I look over to my buddy to signal that I needed to go up, and when I look at him, he is making the same “we need to surface” signal. We start making our way to the surface, and at 107 feet, my buddy starts sinking back down to the surface and his moaning noises is now with every breath. My heart rate according to my chest strap now hits 179 bpm. I kick down, grab his arm and began ascending while holding on to him. He drops his flashlight and planes out for buoyancy control while I hold on to him. At 80 feet I dump all my air and am searching for his deflator button to control his and my ascent. Where my air 2 is color coded, his dump button is black and his inflator button is blue. I knew from right before the dive that his inflator button was blue, but in the dark water, was unable to find the deflator button. I know this is basic level stuff, but the thought to pull his dump valve never even crossed my mind. Holding on to him, I begin fin kicking down to slow the ascent. Our ascent increases from a controlled 45 ft/min to 75ft/min at 20 feet. At around this time, my dive buddy thinking he was deflating hit his inflator button hit his inflator and began an uncontrolled ascent at 125 ft/min. Luckily, his training kicked in and he exhaled all the way to the surface. I let go and he rose to the surface. I looked up and could see that he appeared to be okay, and he quickly descended to 20 feet where we met back up, signaled the “okay” symbol to one another, and began swimming back. I fired off my SMB and we swam back to shore.
When we surfaced, I said, “dude I think we almost died back there”. I felt like we had seconds if not minutes before something went tragically wrong. He told me that he was unaware that I was having any issues at all, and that my “go up” signal was because of what I witnessed him going through. He said that at 120 feet he began seeing bright flashes of light and he was concerned he may lose consciousness. My first thought was we must have gotten bad gas somehow. He also mentioned that he saw me go off my compass heading significantly, so I may have been out of it too.
We have previously dove 30% Nitrox at 120 feet on the USS Oriskany, and our dive planning for this current dive put us at 124 feet MOD for 30% with a max PP02 of 1.4 bar. Meaning, we didn’t think it was the oxygen. We immediately called our friend who has an 02 reader, and were able to meet up with him to confirm we had 30% (3rd 02 check).