Great sounds, could use some polishing.
I'm not a big fan of mouse follow games, but this was a good one.
That having been said, it could be a great one with use just a few minor touches. My 2 cents for version 2 (or 1.1):
-- a little more focus on the score, especially point values appearing when/where you eat the fish
-- improved animation all around, but especially on the shark: open the mouth to eat!
-- multiple lives
Those few would help out a great deal, IMHO. But as I said, a good game! Keep it up!