The main theme of the story is heroism. Santiago makes up for his age with his endurance to withstand hunger, pain and isolation. He does not blame the sharks for snatching the marlin, but he acknowledges that it is his mistake to have ventured far inward into the sea. As a fisher who has caught no fish in 84 days, Santiago is fighting against defeat. However, he does not yield because he moves further into the sea than he has ever sailed before. He struggles with the marlin despite his exhaustion and pain. After catching it, he hopelessly fights off the sharks. Whenever the situation gets difficult and he is threatened with despair, he uses various tactics to stimulate his opposition to defeat: He recollects memories of his strength while he was young through dreams, and sometimes prays to God. Santiago has unlimited potentialities in the presence of danger. His potential is realized when he manages to get the giant marlin. However, the outcome is less significant than the struggle as he also chooses to battle with the sharks. As a result, it is not really important that he brings the marlin home; the important thing is he wins the battle, and after the struggle he becomes a hero.The story’s black hole is “a man can be destroyed but not defeated”. Santiago symbolizes every man's battle to survive. Just like Santiago's attempt to take the marlin to the mainland intact is unsuccessful, no man can escape death. However, through Santiago's struggle, the author illustrates that escaping from death is not the major concern. Santiago sees the words, "a man can be destroyed but not defeated” close to the end of his tussle with the marlin. That is to say, victory over the unavoidable does not define a man. Rather, it is his struggle against the inevitable that defines him.