you should add shark traps for example (2x spears + 5x rope =shark trap)
beds, day/night cycle, torch to scare away shark, more kinds of food, multiplayer server so that you can travel to other peoples rafts with a boat for example,
you should also add a story where you for example have to travel to other rafts/islands in search of a flare gun, when you get the flare gun you can shoot it, but then 5 or 8 sharks attack very often until you get rescued maybe 1 day later.
i know im being very specific but its just a suggestion.