Santiago, an old, weathered fisherman has just gone 84 days without catching a fish. On the 85th day, he is determined to catch a big, impressive fish.

　　For years, Santiago, living in a small fishing village in Cuba, has been fishing with a young boy named Manolin. Manolin started fishing with the old man when he was only 5 years old. Santiago is like Manolin's second father, and has taught the young boy everything about fishing. Manolin's parents, however, force the boy to leave Santiago and fish on a more lucrative fishing boat.

　　He feels the 85th day will be lucky for him. He sets out on his old, rickety skiff. Alone on the water, Santiago sets up his fishing lines with the utmost precision, a skill that other fisherman lack. Finally, a huge Marlin has found Santiago's bait and this sets off a very long struggle between the two. The Marlin is so huge that it drags Santiago beyond all other boats and people . His hands become badly cramped and he is cut and bruised from the force of the fish.Santiago and the Marlin become united out at sea. They are attached to each other physically, and in Santiago's case, emotionally. He sees the fish as his brother. Despite this, Santiago has to kill it. He feels guilty killing a brother, but after an intense struggle in which the fish drags the skiff around in circles, Santiago harpoons the very large fish and hangs it on the side of his boat.

　　For a while , a pack of sharks detects the blood in the water and follow the trail to Santiago's skiff. Santiago has to fend off each shark that goes after his prized catch. Each shark takes a huge bite out of the Marlin, but the old man fends them off, himself now bruised, but alive. He sails back to shore with the carcass of his Marlin. He is barely able to walk and slowly staggers back to his hut, where he falls into bed.

　　The next morning, the boy cries when he looks at Santiago's bruised hands. He said that he would vows to fish with Santiago again.