I have some ideas:
-Contact steam in order to Raft to be added to steam, because I think this is a great game and it will be added to Steam very fast.
-Add more kind of trees and seeds.
-Add new building materials and to get them you must cut rare trees.
-Add flares to call a helicopter to bring materials.
-Add some kind of turret to automate the attack to the shark, and you will need to craft batteries and bullets for its working.
-Bags and Big Bags depending the more materials you use.
AND AN END :D