Santiago is a Cuban fisherman older than Hemingway (age 52) when he wrote the novella. Santiago's wife has died, and he has a daughter who fears he is too old to fish or even live alone much longer. Santiago is a mentor to a young (probably early teenage) boy, Manolin. When the novella begins, the old man has gone 84 straight days without a catch, and, as a result, is the subject of ridicule among the other, younger fishermen.
So says Enotes:
Santiago also loves baseball and occasionally gambles. He identifies with Joe DiMaggio, the great center fielder for the Yankees in the 1940s and 1950s. Santiago admires how DiMaggio, whose father was a fisherman, plays in spite of bone spurs in his feet that cause him pain whenever he runs. As an old man, Santiago must also cope with the physical demands of his job in the face of the infirmities of his aging body. Yet he suffers without complaining, and it is this stoic attitude that has won him much respect in the community.
Unlike the other fishermen, Santiago fishes the right way, and he treats the fish, the sea, and the birds with respect and humility. The younger fishermen cheapen themselves by catching lesser fish just for money, but Santiago dares to be great, to go far out beyond land, and to hook a great marlin.
Santiago's character is revealed most when he is alone battling the marlin and sharks at sea. We see that he is old but still a man of great moral strength and wisdom. He talks to himself, the fish, and the birds not because he is crazy or lonely, but because he treats all of nature as his equal; in fact, he calls the marlin his "brother." Nevertheless, Santiago cannot abide the sharks, for they are scavengers with no dignity.
In the end, Santiago returns to the island with only a carcass, and he carries his mast the way Christ carried the cross. As such, he suffers quietly, with dignity. We, like Manolin, know that Santiago is not defeated, and he will venture out in his boat the next day to fish not for money, but for pride and self-respect.