I love this game, but personally I think that the biggest problem with this game is that its a little like all the other survive-and-craft games out there. One way to make this different, I think, is to take it down the "tower defense" route. Imagine upgrading your raft and weapons, with the sharks getting more frequent and more dangerous. I like the idea of traps ( falling rocks, nets ect. ) maybe? Maybe intense combat with sharks, in the late game.