What significance do the lions on the beach have in The Old Man and the Sea?
When he was younger, Santiago sailed ships to Africa and he remembers seeing lions playing in the surf on the beaches. As he grows older, these memories become dominant in his mind, even more than his late wife. He is somewhat confused about this, but when he dreams about the lions, it brings him comfort:
...he began to dream of the long yellow beach and he saw the first of the lions come down onto it in the early dark and then the other lions came and he rested his chin on the wood of the bows where the ship lay anchored with the evening off-shore breeze and he waited to see if there would be more lions and he was happy.
(Hemingway, The Old Man and the Sea, Google Books)
The lions represent vitality and youth, and their presence in his mind indicate that he is not fully ready to let go of his past, even as he has come to terms with his present. Remembering the lions means that Santiago will not let go of his past because his experiences made him the man he is, not the man he might have been. At the end, when Santiago dreams about the lions, it is in victory over village prejudice; his joyful dream is now symbolic of his own abilities, not only of his past.
Santiago dreams his pleasant dream of the lions at play on the beaches of Africa three times. The first time is the night before he departs on his three-day fishing expedition, the second occurs when he sleeps on the boat for a few hours in the middle of his struggle with the marlin, and the third takes place at the very end of the book. In fact, the sober promise of the triumph and regeneration with which the novella closes is supported by the final image of the lions. Because Santiago associates the lions with his youth, the dream suggests the circular nature of life. Additionally, because Santiago imagines the lions, fierce predators, playing, his dream suggests a harmony between the opposing forces—life and death, love and hate, destruction and regeneration—of nature.