This is a fun, simple game with a charming theme! I personally think the best part is the visuals. Everything, between the characters, environment, and background work well together.
The music matches the visual theme (8/16/whatever bits, simple) and has a pretty nice loop. However, since I died often while playing, it got annoying listening to it restart over and over. An easy way to introduce some variety would be to have the music loop continuously instead of starting the level. This would also make sure each player hears everything you worked hard to compose, instead of just the first 15 seconds!
I liked the touch of the penguin growing in size each time you eat a fish :) I didn't notice it at first because I was trying so hard to avoid them!