Here's the full passage in context:
He always thought of the sea as la mar which is what people call her in Spanish when they love her. Sometimes those who love her say bad things of her but they are always said as though she were a woman. Some of the younger fishermen, those who used buoys as floats for their lines and had motorboats, bought when the shark livers had brought much money, spoke of her as el mar which is masculine. They spoke of her as a contestant or a place or even an enemy. But 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 them. The moon affects her as it does a woman, he thought.
To Santiago, an old man, the sea is feminine, motherly. She is nurturing and has a depth of wisdom. She is to be treated with dignity. She provides him with "brothers," big fish, which is what he repeatedly calls the marlin: "my brother." Yes, she has not been kind to Santiago for 84 straight days and he may curse her, but she is still his mother; he establishes the proper symbiotic relationship with nature.
To the young fisherman, she is masculine, not like a father, but like an enemy of no relation at all. These fisherman fish for shark livers to make a quick buck, and they are like sharks themselves: violent scavengers. They use motorboats (pollutants) and buoys (cheats) and therefore exploit the sea for money only. They only blame her and do not look inside themselves for knowledge as to reasons why she withholds her gifts. They do not love her (or even acknowledge her proper gender). Above all, they do not commune with her, which is the proper relationship between man and nature.