The biggest fish is the biggest challenge. Elaborate.

 The biggest fish is the biggest challenge. Elaborate.

The sentence presents complete symbolism. Hemingway presents the fish as the desire of human being, so the biggest desire is the biggest challenge. The sentence is given from that part of the novel when Santiago was t(ying/sail back to the shore with the hooked huge Marlin. Santiago ventures all alone. He fights with the big fish, Marlin. He uses his full strength, will­power and determination to come back-with, his reward. He fights with sharks which are. the symbol of hurdle in  a .successful life. He wishes to prove his worth against a worthy adversary, the marlin. He says; “1 will show him (Marlin) what a .man can do and what a man endures."
Although the old man is physically weak, yet he is not ready to surrender. Because he wants to catch the big fish which represent the desire or success in the human life. In fact, i life is a constant struggle. The sharks do represent the evil faces. So to get the big desire, we have to fight with big evils or hurdles, as Santiago fights with the sharks with great courage, will-power and determination.