You should add several new fish/other marine animals(or even birds and stuff) to fish up or encounter(like the shark)
Maybe a whale shark that if it bumps into your raft it destroys 1 or 2 segments, or tuna that is between mackerel and shark for eating, maybe some cute little sea otters who will be your pet and catch some fish for you, a sea gull which you can shoot down(using a bow and arrow or throwing spear which could be added), dolphins which distract sharks and jump around in the distance, multiple kinds of sharks such as mako sharks(faster than normal and can jump out of the water a bit), great whites(does more damage per bite), multiple kinds of fish such as cod, haddock or other kinds I can't think of at the moment and maybe... SEALS!
Anything you add to the game though I'm going to enjoy probably!