The central character is an old Cuban fisherman named Santiago, who has not caught a fish for 84 days. The family of his apprentice, Manolin, has forced the boy to leave the old fisherman, though Manolin continues to support him with food and bait. Santiago is a mentor to the boy, who cherishes the old man and the life lessons he imparts. Convinced that his luck must change, Santiago takes his skiff far out into the deep waters of the Gulf Stream, where he soon hooks a giant marlin. With all his great experience and strength, he struggles with the fish for three days, admiring its strength, dignity, and faithfulness to its identity; its destiny is as true as Santiago’s as a fisherman. He finally reels the marlin in and lashes it to his boat.

However, Santiago’s exhausting effort goes for naught. Sharks are drawn to the tethered marlin, and, although Santiago manages to kill a few, the sharks eat the fish, leaving behind only its skeleton. After returning to the harbour, the discouraged Santiago goes to his home to sleep. In the meantime, others see the skeleton tied to his boat and are amazed. A concerned Manolin is relieved to find Santiago alive, and the two agree to go fishing together.