Within the story, the marlin serves many purposes—it’s a symbol, a driving force for the plot, an adversary as well as an ally to Santiago, and a means by which he achieves a sense of enlightenment. The marlin’s very first appearance introduces the literal push-and-pull dynamic that will guide the action for the rest of the novella, characterizing the marlin not as a passive victim but as an active participant in Santiago’s struggle, an opponent worthy of respect and admiration. Santiago catches the fish because it takes his bait, but the marlin is so powerful that it proceeds to pull Santiago’s boat, resisting capture. A surprising relationship forms; by recognizing their mutual drive, labor, and need to survive, Santiago feels empathy for the marlin and comes to view their conflict as a partnership. Essentially, he feels, they are in this together, both fighting with all their might against death. The marlin may be hooked, but Santiago too feels the pain of their struggle as the fishing line cuts into his hands. In this way, both can be considered Christ figures.

After three days and three nights, both are desperate and exhausted. The conflict culminates when the marlin makes one last bid for freedom and Santiago kills it with his harpoon. Even though he has ended the marlin’s life, Santiago’s respect for it is so great that he doesn’t wish to see it sold at market to anyone who wouldn’t likewise respect its magnificence, suggesting the bond between the old man and his prey persists even beyond death. That Santiago continues to regard the marlin so highly suggests there is honor and meaning in death, particularly at the end of a glorious battle between worthy foes. But Santiago doesn’t merely see the marlin as a worthy foe and partner; he identifies with the marlin so strongly that it can be inferred he sees the marlin of an extension of himself—that he and the marlin are, in fact, doubles. Santiago’s battle with the marlin, then, is a battle with his own self. The man and the marlin are linked, just as life and death are. Indeed, Santiago’s unity with the fish, and his respect for it, transcend his sense of self when he says, “Come on and kill me. I do not care who kills who.”

Such is the unity between the two that the marlin’s death foreshadows Santiago’s eventual fate. It’s likely that he won’t have the chance to catch another fish, but the old man realizes there is triumph in death when the marlin “came alive, with his death in him,” suggesting life is cyclical and death brings rebirth. This bittersweet tone is mirrored in the final scene, when Santiago sleeps at last, exhausted, and dreams of lions. For both, the struggle is over, and just as the marlin was victorious in its defeat, so too is Santiago.