My proposal is to insert the boat, a parrot who speaks, warns of the shark or the wreckage of the ship. For parrots you can insert a tree with seeds for the birds as food, a water container. This is possible only when collected, for example, 50 barrels. The wreckage of a ship on the horizon with some animals and natural food options for them when you kill 50 sharks. all this to be possible only when conditions are met