This has nothing to do with retouching, but I thought it was seriously cool, so I'll post it here. This is the most realistic fishtank simulation I've ever seen. And the demo is free!
and extract the file inside. It's only a single 600k file. (Windows only, but a Mac version will be available this spring)
It's an SCR file, but don't get all worried. That's the screensaver suffix. Doubleclick on the file to run it. Press the spacebar and type "testfish" to get rid of the registration info.
Directions on upgrading to the pay version and background information about the program are all available on the website (http://www.serenescreen.com
). This free version isn't practical as a regular screensaver (one of the limitations).
An interesting sidenote: Paintshop Pro was used to paint the textures.