For Santiago, the sea isn't just a large body of water. It isn't just his place of work, a place where he makes a living. It's so much more than that: it's an extension of his soul. Whereas others may look upon the sea as an object of the natural world to be exploited for its riches, Santiago is joined to the shimmering blue by an almost mystical bond. He belongs to the sea as much as it belongs to him.

Unsurprisingly, therefore, Santiago only ever feels at home out there on the water. Even though his job as a fisherman's becoming more and more of a struggle due to his advancing years, he needs to be out there in his boat. The sea is in his blood, and one gets the distinct impression that once he's no longer able to fish, then this life will effectively come to an end.

His latest expedition may not have been a success; in fact, it's been pretty much a disaster. But in the overall scheme of things, that's not what really matters. What matters is that Santiago is still physically able to board his shabby old boat and head out to sea once more. Only there, out among the waves, can he ever feel truly alive.

Santiago relies on the sea for his daily needs. He fishes for a living in the Gulf Stream. However, in the beginning of the story, he has gone eighty-four days without catching any fish. At the behest of his parents, his helper is forced to abandon him. The parents believe that the old man has lost his luck, but the helper feels sad for leaving the old man’s boat.

Santiago does not lose hope and continues to fish. He believes that his fortunes will soon change for the better.

“Tomorrow is going to be a good day with this current,” he said.

The old man loves the sea because he thinks of it as “la mar.” This is the name used to refer to the sea by those who love it. The old man thinks of the sea as a woman who has the ability to grant or withhold fortunes. Although he approaches the sea with high expectations, he is aware that the sea is not entitled to do him any favors.

Santiago is at home when he is at sea, and he identifies with the different creatures, as demonstrated by how he is able to describe them.

Santiago has a unique, loving relationship with the sea. He depends on his coexistence with the natural environment of the ocean to make his living. Santiago refers to the sea as la mar, which is a Spanish term of endearment. Santiago views the sea as a woman who is capable of giving or withholding rewards. He respects and reveres the sea throughout the novella and is able to interpret signs from the natural environment. Unlike the newer generation of fishermen, who rely on technology and modern techniques to catch fish, Santiago relies on the organic, traditional methods of fishing. Despite his recent bad luck, Santiago is an experienced fisherman who understands the sea and the creatures in it. He feels as if he is an intrinsic part of the ocean and recognizes his kinship with all of the sea's living creatures. The sea spiritually enriches Santiago and gives his life meaning. His role in life is connected to the sea, which is a fundamental part of his existence. 

Santiago's relationship with the sea is essentially an existential one; he exists because of the sea that provides him with food, as a fisherman, his being is defined by his relationship with the sea, and his happiness and sorrow depend upon his successes and failures on the sea.  Indeed, it is the sea that is Santiago's essence and gives meaning to his life. 

Because of this inextricable, but variegated connection to the sea, Santiago anthropomorphizes the sea as "La Mer" which is what people call it in Spanish when they love the ocean:

...the old man always thought of her as feminine and as something that gave or withheld great favours, and if she did wild or wicked things it was because she could not help....

Therefore, since Santiago conceives of the ocean as the source of life and meaning, the struggle of the old man with the fish in the sea becomes a metaphor for the existential struggle of man in life. Having gone eighty-four days without a catch, Santiago is viewed by the other fishermen as "unlucky," cursed, and a failure. That is, with his life threatened by starvation, Santiago's existence has little meaning. However, when he catches the great Marlin, Santiago is renewed in his manhood, his life regains its meaning and value. Because Santiago's hope and luck is renewed, even though the shark steals the meat of the fish, he can still dream of the lions and hope.