While at sea on the second day of Hemingway's narrative, Santiago sees the respected sea turtles who venture forth bravely to eat the poisonous jellyfish. Closing their eyes so that they are carapaced, the heroic turtles eat the jellyfish filaments and all, bravely doing what they must to eat. Likewise, the determined Santiago goes forth onto his beloved sea, la mer, facing whatever dangers he must in order to eat. For, the sea feeds him, as well.
As he admires the turtles, despite his having worked on turtle boats for many years, Santiago feels a sympathy for them, understanding that they, like him, venture forth and seek food dangerously because they must. Yet, he is unlike them because they are truly a part of the sea while he is only at sea in a boat. Yet, they have been cut up by man, as he has and his heart has had to beat outside his body figuratively just as the turtle's will do so in reality when they are captured and killed for food. Watching the turtles seek their prey, Santiago thinks,
Most people are heartless about turtles because a turtle's heart will beat for hours after he has been cut up and butchered. But...I have such a heart too and my feet and hands are like theirs.
Santiago's hands are rough and cut by the sea; like the turtles he is steady and persistent in going after his catch. And, like the turtles, his heart must sometimes beat "outside" his body when he fails to catch anything, or when others taunt him. Although old, Santiago is hardy like the old loggerhead turtles; still, he is not a real part of the sea as are the eternal turtles.