What is The old man and the sea?

This is the book called the old man and the sea, it written by Ernest Hemingway in the 1950's. It is about an old Cuban fisherman called Santiago who has a 3 day "battle" with a marlin before he manages to catch it but the marlin is then eaten by sharks as Santiago is taking it back to land. At the end of the novel it suggests that Santiago dies from the struggle with the marlin because he feels something in his chest has broken and that something is his heart.