Santiago is beat up by the ordeal of catching the fish, and tries to keep his head clear as he begins the trip home. For a moment he wonders if it is he bringing in the fish, or the fish bringing in him, as the huge fish, bound to the side of the boat, seems to sail alongside as an equal.
Only an hour into his return trip, sharks attack. The old man's head is clear now and "he is full of resolution but he (has) little hope". As he engages in mortal battle with the shark, he knows that he must think, use his sense of reason in fighting, because it is the only advantage he has over the shark. He then ruminates about the nature of sin, going back and forth in his mind on whether or not it was a sin to kill the fish. He knows that he loved the fish when it was alive, which would make his action in killing him not a sin, but he also knows that he killed to fish partly out of pride. Santiago does not fully understand about the nature of sin, but concludes that he killed the fish in order to survive, out of self-defense in a way, and that he "killed him well".
Santiago resolves to fight to the end, even when it is clear that the battle with the sharks is lost. When the fish is all but gone, he for awhile "sail(s) lightly...and (has) no thoughts nor any feelings of any kind...he (is) past everything now and he sail(s) the skiff to make his home port as well and as intelligently as he (can)". He then begins to think about the wind and the sea, and his friends and enemies in the sea, and realizes that it "is easy when you are beaten". He wonders for a moment what it was exactly that had beaten him, and concludes that he was not beaten at all, he had just "(gone) out too far".