Explain the irony of rainsford thoughts: "all he knew was that he was safe from his enemy, the sea ... "

Although at the moment, it may seem as if Rainsford's enemy is the sea, he soon realizes that that is not the case. He is hunted by Zaroff, a hunter hungry for intelligent prey, on his terrifying island. Then, at the end of the short story, Rainsford jumps into the water, escaping Zaroff and winning the game. It is ironic because his "enemy" is what saved his life.