How to Paint a Dark Underwater Scene(Beginner Level)(oil)

Paint subject first, then paint background water colours,. Fill in the ground area with colour and shapes instead of defined plants, rocks and so on. Lines of white across the top of water will create the effect of being underwater.
Paints used: Phthalo green (mix with value three gray), Turquoise (mix with value five gray), Black, Titanium White, Cadmium Yellow Light, Indian Red,
Have Fun!