While Santiago was unfortunate enough to lose his harpoon after stabbing the mako shark, he manages to create a new spear by tying his knife to the boat's oar. Later, the blade of the knife snaps while he is stabbing a shovel-nosed shark and he is without a bladed weapon again for the rest of his trip.
A reader cannot help but feel sympathy for Santiago as he tries desperately to fight off the many sharks who surround him and the marlin. In addition to using his harpoon and then his makeshift spear, he also clubs several of the sharks with the oar as well. Clearly, this was a battle he could not win without any weapons and being so greatly outnumbered.