Multiplayer? idk i think with a good bit of additions and a harder gameplay mechanic multiplayer would be fun and interesting maybe with voice but at least with text so you can possibly set up a way to communicate via vice like dicord or skype but have public and private options with 1 or more rafts that you would have to connect (if multiple) or transport boats for trade if you decide not to connect. with 2 rafts there would be the idea of glitches happening with sharks locking on tho structures how many there would be etc
but i think multiplayer could be very cool especially with higher difficulty and maybe different modes or game varients