I say surpsingly only because it started off really hard to catch the hang of, with the unusual darting movements, but then became much easier to deal with. Given the way it moves, I'd suggest making the "hero" icon a fish instead of a star simply because it darts in that quick way small fish have and fits the them better. Not a complaint, mind you, just personal taste.
If there's one thing I'd criticize, it's the huge abundance of bubbles at the beginning while the player is still at the point where they're catching on. Making it a little sparser might make the learning curve a touch easier. Not a serious issue, and again, nothing I'd dock rating points for.
Overall, entertaining game. Thanks for sharing it.