Great suggestions, appreciate that. For some reason it's so tempting to submit now even though there's so much time left. I'm going to resist and try to keep improving it.
I'm using assets from a licence free game on GitHub. I haven't created a single piece or art, I've always neglected that skill, which limits my games quite a bit. I'd love to have other fish options but I can't draw them :/
But I do want to make the water seem more like water, rather than a flat background. Thanks for the suggestions, and the pixel art in your game is actually really good, I like it.