Alright, finally got some time to try the game out. First off, great job on the art. It's very appealing and atmospheric. The aesthetic is very pleasing. However, when designing the fish that are going to be eaten, I think you should take a close look at how they're designed. There were two fish in particular that it looked like I shouldn't be going after. Both had kind of an evil grin which made me think they were poisonous or something along those lines. But it turned out everything on screen was ok to eat.
I don't know how far into development you are, but I suggest adding more mechanics to the gameplay if you're not too deep in. As I mentioned above, some fish look like they could poison you. So perhaps some fish that decrease your health should be added?
And one final thing was that upon contact with the shark, fish are automatically eaten no matter where contact is made. I think it needs to be that they are only eaten when they go near the shark's mouth. There were times where I hit them with my tail fin and it considered them eaten.