Once upon a time, San Diego (Spencer Spencer Tracy) was the best fisherman in the area, and it was impossible for him to return empty-handed as long as he attacked the sea. But now, Santiago is getting old, and he understands that the situation is not optimistic after months of grain failure. In the face of peer questioning and ridicule, Santiago is calm on the surface, but secretly anxious in the heart. In order to catch fish, San Diego came to a strange area of water, where he found a "big guy". Then, San Diego fought with the big guy in the water for several rounds and finally caught it. Soon, the smell of blood in the water attracted groups of sharks, in order to protect their trophies, in order to protect their honor, San Diego launched a life-and-death struggle with sharks.