So after the disaster of yesterday, I appealed to my friends for a fail-proof idea. Natalia suggested the saran-wrap method, which I have yet to try.
It occurred to me that if I chose shades of blue and green, it might look like sea water. And so I gave it a shot, and added a fish to match. :)
The fish is done with Sally Hansen - Orange Impulse, with apparently invisible hints of Brash - Gone Bananas. I finished that off with Kiss's black striper for the eye, and dotted on some bubbles with Sally Hansen - Platinum.
And just to try to show why it reminds me of water, here's a picture of my hand in water: