Would love a bigger ship, with living quarters. A more self sustaining vessel. Give me more to do in the ocean. How about... bestial mermaids? (and let me tame them) xD
Triton suit? let me swim without restriction, possibly dive, I love corals. underwater cave/dungeon with air pockets? A form of interaction with corals (not mining), maybe make so corals spawn a lot of fishes. Or something else.