Two connections come to mind: one contemporary and one Biblical.
Hemingway wrote the novella in the 1950s, near the end of his career. Santiago also is near the end of his career, as was Joe DiMaggio, the baseball player. Hemingway, like Santiago and DiMaggio, was fighting pain and old age while also trying to achieve one last great achievement. Hemingway suffered from depression (he would eventually commit suicide), while Santiago has problems with his hands and DiMaggio suffered pain bone spurs. Just as Santiago is trying to go far out, catch a great fish, and bring it ashore, so too was Hemingway trying to write a novella that was both personal and allegorical. But just as the fish is devoured by sharks, so too was Hemingway frustrated with his finished book (even though it did win him a Pulitzer).
Another connection is Biblical: Hemingway's style is simple and honest, much like a parable. Santiago is both a Jonah (Old Testament) and Christ (New Testament) figure. Santiago is meant to suffer in the novella, and his courage in the face of suffering is a testament to Manolin, his disciple. Santiago's battle with the great fish allows his to become an even more humble servant to humankind.