Santiago (the old man) and Manolin (the boy) speak in a conversational style, simply and efficiently, saying what is on their minds without embellishment. Their dialogue is meant to evoke the period and location of the story, which is set in Cuba. Using English, Spanish, and Cuban idioms, as well as speaking of baseball (an international pastime during the 1950s) serve to root the story in a present-day, realistic setting.
"When I was your age I was before the mast on a square rigged ship that ran to Africa and I have seen lions on the beaches in the evening."
"I know. You told me."
"Should we talk about Africa or about baseball?"
"Baseball I think," the boy said.
(Hemingway, The Old Man and the Sea, Google Books)
With this loose, informal dialogue, Hemingway establishes both Sanitago and Manolin as people comfortable in their own personalities, and without the need to make excessive or exaggerated statements to show their emotions. In fact, since so much of the dialogue is seemingly "emotionless," the true emotions felt by both characters is left to be inferred by their actions, and by the great respect and love they have for each other.