The art style is very clean and cohesive!
Enjoyed the gameplay, too, understanding that it's something that had limited time for development. Had the same <null> thing happen before I could get my harpoon upgraded enough to make further progress.
Generally agreed about the more player input component: would be nice to have sort of, idk, balance bar or mini-game-styled element for completing the catch of a fish. Two ideas that come to mind are from RPGS, e.g. a bar that you have to move to match the movement of the fish (Breath of Fire III) or a button mash kind of deal where you have to hit the button fast enough before the fish pulls away from your line. Or maybe button combinations?
Either way I think it's a good starting point!