Interesting concept! (I played the current/non-gamejam version)
Some random ideas that popped up while playing:
I can't quite tell if the idea is for this to be a kind of relaxing "sandbox" or more a score chasing game.
Sandbox, would be cool if the ocean floor was "revitalized" as you remove trash (something simple as changing the color of the texture or maybe even add some coral textures or something). Also, upgrades! :)
If it's a score chaser, maybe add score for each bucket based on how many pieces of trash you pick up at once? Another idea; limit the amount of trash at the start and have boats or something dump trash so you get to chase the trash around.