As the old man battles to first bring in the fish he has hooked and then to try and get it to the shore without exhausting his last reserves of strength, he is repeatedly destroyed in small pieces. First he is worn very thin and weary by the long chase and all of the actions he must take in order to draw the fish to the boat. His hands are torn to pieces and he grows very hungry and thirsty as he runs out of provisions. The sharks soon begin to tear at the very fish that he spent so much time and energy bringing in. Eventually they have basically taken everything of value, destroying the man and his boat and the fish in the process.
Yet the struggle and the will of the man to continue are not defeated, he has gained a victory even as the thing for which he fought was destroyed, even as he was destroyed.