Ernest Hemingway was apparently telling his own story through the experience of Santiago. Hemingway was getting to be an old man himself. He was living in Cuba and must have seen the native Cuban fisherman going out in their boats every day. Hemingway loved fishing for marlin. He had a high-powered boat named Pilar, after a tough female character in his novel For Whom the Bell Tolls. There is a strong and obvious analogy between Hemingway and Santiago. The Cuban fisherman had been unable to catch a big fish for a long time and was feeling depressed and old. Hemingway had been regarded as the best American fiction writer and one of the best writers in the world. But he was beginning to lose confidence in himself. He desperately wanted to write another novel that would show the world, and himself, he was still a champion. It had been many years since he had written a successful and critically acclaimed novel. According to the eNotes Introduction in the Study Guide for The Old Man and the Sea:
When The Old Man and the Sea was published in 1952 to wide critical acclaim, it had been twelve years since Ernest Hemingway's previous critical success, For Whom the Bell Tolls. His major writing effort during the intervening period, Across the River and Into the Trees, published in 1950, had been widely dismissed as a near parody of the author's usual style and themes.
Perceptive readers saw the allegorical elements in the story of Santiago. The big fish symbolized the big novel Hemingway wanted to write if only he could still come up with the necessary iinspiration. The sharks that ate most of Santiago's marlin symbolized two things for Hemingway: (1) they symbolized all the hundreds, or possibly the thousands, of mediocre writers who were imitating Hemingway's famous style, thereby inevitably causing him to appear to be imitating himself; and (2) the sharks symbolized the critics, many of whom delighted in seeing Hemingway apparently losing his inspiration, his celebrated "luck," and his nerve.
It happened that Hemingway loved fishing for marlin. With The Old Man and the Sea he shows his deep knowledge of the sea, the big fish, and the brave men whose livelihoods depend on catching them with their crude equipment in their flimsy boats. The story was an enormous success. Hemingway had found the one big idea he so badly needed. He wrote because he was born to be a writer. In 1961, when he believed he could not write anymore because of severe depression, he committed suicide.