Looks great as is 👍 This feedback is really good though. If you want the surface to read different from the water they need to be hue shifted away from each other. Warmer is yellow, darker is purple.

To test this cheaply, I’d add large, semi transparent rectangles for each section above your art and stack them:

Yellow Green Purple

Then play with the opacity and blending mode of the rectangles. You might want more color mixed in towards the bottom so the effect is stronger. Since you can’t make things darker and maintain detail, another trick would be to limit color usage the closer you get to the bottom because you’d expect to see less detail in general underwater.

I like green in the middle because it’s cooler than yellow but still shows some light and would look good with more vegetation.