Quick update, since I'll probably be hitting the sack soon.
-Added some effects for when a harpoon hits the water (makes a splash and slows the harpoon down)
-Added the first fish! (As well as the infrastructure to add lots more types very quickly)
-The harpoon collides with the fish, causes a blood explosion, and the harpoon sticks in them
Next: Figuring out how to make a 2D rope, for reeling in. This could be tricky...