All I remember is that the old man caught a big fish but by the time he got back to shore not much of it was left. I don’t know if it is meant to be an allegory for something or just a simple story. Also that Hemingway tells us that when the old man got up in the morning he went outside to take a leak. Most novelists ignore that sort of thing. Maybe it is meant to show he is an authentic old man with an enlarged prostate.
South Park did a great summary.