Maybe add in the chance to get bumped by a whale on occasion, shaking free coconuts and damaging foundations. Have risk of an albatross (huge bird which can and does cross huge expanses of ocean without stop) swooping in and snatching any fish/shark meat cooking without a floor above it (later in the game, so it's not too difficult to get food early on-- maybe after killing the second shark). Occasional "special" items in barrels would be cool, too, even if they're just decorative-- break up the monotony of the place.