Santiago notices the bird again, and suspects that he has found fish. Soon after, the old man sees a tuna leap from the water and the bird dives to catch the bait fish stirred up by the tuna's jump. Santiago gently moves toward the school and soon feels a bite. He pulls the albacore in the boat and clubs him to death.
The old man soon realizes that he is talking to himself. "It was considered a virtue not to talk unnecessarily at sea and the old man had always considered it so and respected it. But now he said his thoughts aloud many times since there was no one that they could annoy" (39). Santiago recalls himself from such thinking, saying "Now is the time to think of only one thing. That which I was born for" (40). Soon, there, is a strong bite on one of the lines Santiago cast out earlier.
Santiago notices a bite on his hundred-fathom-deep line. The first bite is hard, and the stick to which the line is connected drops sharply. The next tug is more tentative, but Santiago knows exactly what it is. "One hundred fathoms down a marlin was eating the sardines that covered the point and the shank of the hook where the hand-forged hook projected from the head of the small tuna" (41). Encouraged by a bite at so deep a depth so far out in the Gulf, Santiago reasons that the fish much be very large.
The marlin nibbles around the hook for some time, refusing to take the bait fully. Santiago speaks aloud, as if to cajole the fish into accepting the bait. He says, "Come on... Make another turn. Just smell them. Aren't they lovely? Eat them good now and then there is the tuna. Hard and cold and lovely. Don't be shy fish. Eat them" (42). After many false bites, the marlin finally takes the tuna and pulls out a great length of line.
Santiago waits a bit for the marlin to swallow the hook and then pulls hard on the line to bring the marlin up to the surface. The fish is strong, though, and does not come up. Instead, he swims away, dragging the old man and his skiff along behind. Santiago wishes he had Manolin with him to help. Alone, though, he must let the fish take the line it wants or risk losing it. Eventually, the fish will tire itself out and die. "But four hours later the fish was still swimming steadily out to sea, towing the skiff, and the old man was still braced solidly with the line across his back" (45).
As the sun goes down, the marlin continues on in the same direction, and Santiago loses sight of land altogether. The result is a curious stalemate. As Santiago says, "I can do nothing with him and he can do nothing with me....Not as long as he keeps this up" (47). He wishes for the boy again and muses that "no one should be alone in their old age....But it is unavoidable" (48). As if in response to this expression of loneliness, two porpoises come to the surface. Seeing the frolicking couple, Santiago remarks, "They are good....They play and make jokes and love one another. They are our brothers like the flying fish" (48). Santiago then remembers a female marlin he and Manolin caught. The male marlin had stayed beside the boat in despair, leaping in the air to see his mate in the boat before he disappeared into the deep ocean. It was the saddest thing Santiago had ever seen.
Something then takes one of the baits behind Santiago, but he cuts the line order to avoid distraction from the marlin, wishing Manolin was there to watch the other lines. Expressing his resolve, Santiago says, "Fish... I'll stay with you until I am dead" (52). He expresses ambivalence over whether he wants the fish to jump, wanting to end the struggle as quickly as possible but worrying that the hook might slip out of the fish's mouth. Echoing his former resolve though with less certainty, Santiago says, "Fish... I love you and respect you very much. But I will kill you dead before this day ends" (54).
That the fishermen call all the fish tuna and only differentiate between them when they sell them is at once a statement of the theme of unity and a repudiation of the market. It is not ignorance that underlies this practice, but rather a simplifying appreciation of the unity of the sea. There are fish and there are fisherman; those who are caught and those who catch. This distillation of parts heightens the allegorical quality of the novel. The market forces the fisherman to forget this symbolic binary relationship and focus on differentiation, requiring a multiplication of the terms of difference. As the novella stakes out a position of privileging unity, this market-driven divisionism come across negatively. This makes sense in light of Hemingway's previously mentioned anger at the unappreciative literary audience for his previous effort.
Hemingway's description of the marlin's initial nibbling on the bait utilizes the same phrases again and again, e.g. "delicate pulling." While this may express the actual event perfectly, the repetition creates a distancing effect, pushing the prose more toward poetry and less towards realistic objectivity. This heightens the allegorical quality of the narrative, which, at least explicitly, Hemingway denied.
The response with which Santiago's thoughts of loneliness are met is another expression of the theme of unity in the novella. Santiago thinks to himself, "No one should be alone in their old age....But it is unavoidable" (48). As if in response to this, Hemingway introduces a pair of friendly dolphins in the very next paragraph. "They are good," says Santiago. "They make jokes and love on another. They are our brothers like the flying fish" (48).
Santiago begins to feel sorry for the marlin he has hooked. This pity for the great fish is intensified when Santiago recalls seeing the misery of a male marlin after he had caught its mate. Suddenly, Santiago is speaking of his actions as "treachery," an odd word for a fisherman to use in describing his trade. The more he identifies with the sea and its creatures, the more despicable his actions become. Soon, though, Santiago's treachery is transformed from his act of killing to his having gone out further than most fisherman go.
The image of a struggle between two figures alone in the great "beyond" certainly conjures an air of monumental conflict. This heroic angle is played up even more when Santiago ends these reflections by thinking, "Perhaps I should not have been a fisherman....But that was the thing I was born for" (50). Again, this emphasis on fate is typical of heroic stories, especially tragedies.
Santiago's identification with and affection for the marlin increases the longer he is with the fish. In order to convince the fish to be caught and to steel himself for his difficult task, Santiago says, "Fish... I love you and respect you very much. But I will kill you before this day ends" (54). Soon after, Santiago tells the bird that has landed on his boat that he cannot help because he is "with a friend" (55). And later, Santiago goes as far as to wish that he could feed the marlin, calling it his brother.