As the fish tows the boat, Santiago wonders what he'll do if the fish suddenly dives down deep and then dies. But he immediately assures himself that there are plenty of things he can do. He thinks about how he hooked the fish at noon and has been holding onto the line for four hours but hasn't yet had a first glimpse of the fish. Santiago drinks a bit of water from a bottle he has tucked away in the bow and tries not to think, but simply endure. When he realizes he can no longer see anything of the land, he reminds himself that he can always sail back by following the glow coming from Havana at night. Then he ponders various times when the fish might come up so he can see it.
After the sun goes down, Santiago ties the dried sack that had covered the bait box around his neck, so the sack hangs down his back and serves as a cushion under the fish line. In the dark, the line looks like a phosphorescent streak in the water. Then he checks the boat's course. Although the fish had been pulling the boat to the northwest, Santiago realizes that the current must be carrying them eastward now. He considers that if he loses the glare of Havana, then they must be going more eastward. Santiago briefly wonders about the results of the baseball game today and wishes he had a radio but then snaps himself up, scolding himself to keep his mind on what he's doing: "You must do nothing stupid." Again, Santiago says aloud, "I wish I had the boy. To help me and to see this." He thinks that, although no one should be alone in old age, it's unavoidable. Then he reminds himself to eat the tuna he caught earlier before it spoils, to keep himself strong.
When two porpoises come playing around the boat, Santiago speaks of them as "our brothers like the flying fish." Then he begins to pity the marlin, which is stronger and stranger than any fish he has ever hooked. Santiago considers whether the marlin has been hooked before, how the marlin cannot know that its adversary is only one old man, what price it may bring in the market, how it pulls like a male and without panic, and whether it has plans or is simply as desperate as he is.
