A commonplace among literary authorities is that a work of truly great literature invites reading on multiple levels or re-reading at various stages in the reader's life. At each of these readings, the enduring work presumably yields extended interpretations and expanded meanings. Certainly, The Old Man and the Sea fits that description. The novella invites, even demands, reading on multiple levels.
For example, readers can receive the novella as an engaging and realistic story of Santiago, the old man; Manolin, the young man who loves him; and Santiago's last and greatest battle with a giant marlin. Indeed, Hemingway himself insisted that the story was about a real man and a real fish. Critics have pointed to Hemingway's earlier essay — which mentions a presumably real fisherman who travels far out to sea in a small boat, catches a great fish, and then loses it to sharks — as the seed from which the novella springs.
However, the novella also clearly fits into the category of allegory — a story with a surface meaning and one or more under-the-surface meanings; a narrative form so ancient and natural to the human mind as to be universal; a form found in pagan mythology, in both Testaments of the Bible, and in Classical to Post-Modern literature. Likewise, the characters become much more than themselves or even types — they become archetypes (universal representations inherited from the collective consciousness of our ancestors and the fundamental facts of human existence).
From this perspective, Santiago is mentor, spiritual father, old man, or old age; and Manolin is pupil, son, boy, or youth. Santiago is the great fisherman and Manolin his apprentice — both dedicated to fishing as a way of life that they were born to and a calling that is spiritually enriching and part of the organic whole of the natural world. Santiago, as the greatest of such fishermen and the embodiment of their philosophy, becomes a solitary human representative to the natural world. He accepts the inevitability of the natural order, in which all creatures are both predator and prey, but recognizes that all creatures also nourish one another. He accepts the natural cycle of human existence as part of that natural order, but finds within himself the imagination and inspiration to endure his greatest struggle and achieve the intangibles that can redeem his individual life so that even when destroyed he can remain undefeated.
In living according to his own code of behavior, accepting the natural order and cycle of life, struggling and enduring and redeeming his individual existence through his life's work, and then passing on to the next generation everything he values, Santiago becomes an everyman (an archetypal representation of the human condition). His story becomes everyone's story and, as such, becomes genuinely uplifting. As the tourists who mistake the marlin for a shark still comprehend from its skeleton something of the great fish's grandeur, readers of different ages and levels of understanding can find something inspirational in this story — perhaps even more if they dip into its waters more than once.