the game is cool but gets repetitive very fast so i tough about a few ideas to make it better

fishes could be different from each other for example some fishes could be heavier and bounce less or be as the normal fish but moving faster

you could unlock different fishes by getting a highscore  high enough or something and you could disable them in a menu

there could be skins for the platform that could be unlocked like the fishes, by doing quests or just getting points

you could make bosses appear every x normal fishes and they would have different mechanics like feeding them a special kind of fish that would be very rare and until you find one the boss gives you a curse 

a menu showing every bosses you fighted against and when you beat all of them a button would appear in the menu and if you click on it the next game you start a secret boss would appear

-some hands

-some nobody

-he's done?

-yes he isn't

-oof