(Android Market link)
We've been working on this one on and off for over a month. It's still got some features I'd like to add, but the current version's already very good looking with some beautiful water surface response, so I think it's time it went out and met the world.
Koi is exactly what it sounds like -- colorful fish exploring their pond. You can customize your fish population similar to Aquarium, can select from ten different backgrounds, and can double-tap to feed your koi. Plus, you can interact with the water surface. It even fully supports multitouch! If you explore the settings you can also enable raindrops and pressure sensitivit.
This turned out very well in my opinion, and I'm excited to hear what folks think!