What are the effects of Santiago's struggles in proving his existence?
Santiago may be viewed as a summative/typical Hemingway. He sets out doing what he does well and he follows all the "rules" of fishing. He happens to catch the largest fish of his life. He "treats" it with respect and takes no joy in the catch, knowing that the fish is a noble example of nature as is he. After the struggle, which his carried on with great nobility on both ends, he catches the fish and lashes it to his boat. This is really all that counts. He loses the fish on the way in as sharks attack the now dead fish and devour it. This is the way it is in Hemingway's world. You "know" it's going to happen, and you don't complain about it because you have no control over things like the sharks. You do have contol over howyour comport yourself in this world, and that's what counts.
Santiago actualizes his existence by living by the rules, behaving "well," and accepting the consequences of living in a world that is not tailor made for us.