I have a few, a threat other than the shark; something a little more unique, and maybe some defenses to prevent said threats from destroying your Raft. Right now it feels like having to stick the shark with a spear every so often is just annoying micromanagement.
Maybe make the furniture be functional instead of straight up cosmetic down the line, and of course, the more aesthetically pleasing things to build the better.
I also feel the current way of getting materials needs an update, given the early development stage of the game it works for now; but we need something like... Well, why not let your raft actually float out instead of being stationary?
Like, come across wreckage from other ships and so on; and give us a way to anchor our raft, either with a straight up anchor of sorts or a way to pin it to other wreckage, like a harpoon gun with a rope attachment. And, obviously the bigger your raft, the more of an anchor you'll need. Give us a little exploration and the game will go a long way. I feel like this idea will help preserve the game's uniqueness and set it apart from other stranded survival games, while giving the players more things to do; and a more unique method of gathering materials other than just fishing for them with nets and your hook.