Importance of knife

Mafatu carves a 10-inch long knife from the rib bone of a whale. It is very sharp, and he uses all of his skill to create it with care. Mafatu uses the knife to kill the hammerhead shark and save Uri when his dog falls into the ocean. The knife falls into the ocean at a later point, and Mafatu dives far down to retrieve it. He is attacked by a large octopus from the reef, and manages to save himself by stabbing it in the eye with his knife.