Fun shooting mechanics, felt good to mow down hordes of fish. I did find that the bullet explosion particles were a little big, they made it hard to see what was going on sometimes. Also the powerups were hard to get, it was always sad when they floated away, so some way to get those easier like a harpoon gun might have been cool.
Actually, are there other weapons? The cooldown bar on the bottom right made me think there were, but I never saw any, just some powerups.
Overall, nice game, I liked it.