symbols in the old man and the sea

You might consider that Manolin's name means "little hand." There is a theme in epic literature (and, as I have argued elsewhere, this novel is an epic!) of the father passing his skill and knowledge to a son, handing it down, we say in English. Though Manolin is not the blood son of Santiago, he is a symbolic son, and probably sees Santiago as more of a father than his own father.
Santiago has a cramp in the boat. He wishes at that point that he had the boy with him. Manolin represents the helping hand of the man. The word is based on the Spanish word for hand: mano.
Interestingly enough, the word mano in Mexican Spa...