Thanks for the great feedback!
Yeeee I probably spent far too much time on the water physics xD, but I'm glad a lot of people are appreciating it as much as I do.
For movement and the speargun mechanics, I was leaning more on the realism side. Originally wanted to make the swimming more complicated and involved, but I remembered water levels suck and scrapped what I had for standard platformer game feel. If I had more time, I would expanded more on the swimming to be like DKC.
Fish spawning was a bit of a late addition for me, originally was going to have a much bigger world with specific fish placements, but didn't have enough time. To be honest, AI pathfinding and logic is one of my least favorite things to code xD, so I opted for complete random movement simple run direction math.