The theme of death is constant in Hemingway's stories, in this particular one we can clearly deduct that the tragedy is not that the hero Schatz is foomed but that he believes himself to be doomed when he is in fact perfectly fine.
Schatz heroism is demonstrated through his words and actions, the abrupt change in his demeanor between day one and the next day being the most dramatic manifestation of it.
Another element is his father's behavior which unintentionally affects and worsens Schatz' mental turmoil. The justapoxition of his father behavior and Schatz' self controlled and tragic stoicism is exactly what Hemingway so cleverly used to portray the main character's heroism.
Hope this helps!
