This game is pretty cool, I would love increased amount of shark. When you killed 2-3 sharks, then they are two instead of one, then three... Different size of sharks, some sharks often try to jump from water to eat your toes (one tile distance) instead of eating the raft.
Killing shark give metals (because we lack some when coconuts tree give plenty of everything else...) would increase the goal of killing some.
Maybe one item to go deeper in water and gather new rare ressource or new food or maybe a kind of net to gather shellfish.
Of course, we want more things to build.
Maybe a day/night cycle with much more attacks during the day and none during the night (then add jellyfish at night or some kind of dangerous animals)