Put difficulty because in 20 minutes the game is too easy... add 2 more sharks who turn around and its good .... (i dont speak english) and decrease the number of objects in the sea
This game does have some great bones. Its a different concept then most when it comes to survival games.
Adding to the difficulty either in mode or timing would be a nice addition.
There could always be new hostile mobs that show up/different types or numbers of sharks. Changes in your environment such as a storm/heatwave/waves could also add to the experience. During the environments changes it could be easier to collect certain items while harder for others. For example a heat wave could make it harder to grow tree's/plants. Maybe if its a storm and raining plants grow better but its harder to catch fish and the aggressive mobs are more annoyed/active.
These are all just suggestions, so far the game is rather enjoyable and I love the concept. Keep it up<3
Oh yeah, day/night cycles and those storms would be a very nice addition indeed. And maybe a bloodmoon of some sort, to prepare yourself for it, that on bloodmoon everything turns red (due of the moon), the water is like blood and the shark population has 3 or 4. And some birds flying around when you are close to an island so you know which direction you should build towards.
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.