What are the odds that the guy at the end is also a Roman agent? The waters there are supposedly infested with sharks and he was wounded. Plus the ship must have been quite a distance from Syracuse when it was attacked since they couldn't possibly run the Roman blockade with one ship.
What are the odds that a man could escape the Roman marines, swim a long distance through shark infested waters while wounded, in the right direction towards Sicily and actually walk to the gates of Syracuse?