There are lots of ideas so let's get started and let me in the comments what do you think or add more.LOVE THIS GAME !
SPECIAL : Weekly updates like "The Forest"
1. Add waves and make the raft "float",move up and down with the water. Also why not Rogue Waves for a developed version where your Raft can be damaged.
2. Add NPCs : more sharks, bigger sharks, whales, trading posts on islands, birds, shipwrecked humans that you help.
3. A story when you start the game to tell you how on earth you got there ? Without any endings or such.
4. Achievements for building, acquiring, killing,etc...
5. Clothes made of shark skin (later updates maybe of gold that you gather from islands)
6. Add day/night cycle, rain, thunderstorm places where you leave the raft (they said the raft will me mobile:D) and gather very rare materials protected by Ancient Pigs with Golden Swords and then show off at others. Also whirlpools that you should avoid.
7. Climate and seasons when more materials come or they don't at all.
8. Furniture : bed, blinds, curtains, torch lamp...