After catching the huge marlin, Santiago is unable to reel him in and must afford him more line. On the fourth day, Santiago realizes that the fish is larger than two others that he has caught weighing a thousand pounds as he has seen it roll on its side a couple of times. In fact, it is longer than his boat. With each turn that the great fish makes, it shortens the line and Santiago sweats as he prepares to throw his harpoon,
But I must get him close, close, close, he thought. I musn't try for the head. I must get the heart.
"Be calm and be strong, old man," he said.
Santiago fears that the marlin may kill him, too. But, he admires the fish so much that he tells the fish he has a right to kill him because of his majesty.
The old man...lifted the harpoon as high as he could and drove it down...into the fish's side just behind the great chest fin that rose high....He felt the iron go in and he leaned on it and...pushed all his weight after it.
Of course, striking the marlin in the heart causes more bleeding than killing it by injuring the head. This bleeding is what brings the sharks, who eventually eat all the marlin. Nevertheless, Santiago prevails as he survives the ordeal and brings in evidence of his victory over the marlin--"defeated, but not destroyed."