The game is pretty cool, but after 2hrs, you have nothing else to do.
I don't know, and couldn't find if there is any endgame, like survive a certain amount of days, or get to land.
My suggestion to make it more enjoyable and last longer:
Add more attributes to the player, apart for food, water and health.
I would add sleep, so you have to sleep on the night, or whenever you want. If the bar gets depleted, you start losing your health. You could sleep on the raft, or craft a bed, so that you fill up the bar more quickly.
Another one could be temperature, so that if you're too hot, you have to go under shade, or if you are too cold, you have to go inside an light a fire.
More weapons would be cool too, nothing too fancy, a bow an arrows would be nice, and it would give use to all the scrap