The Captain The unnamed Captain of an unnamed ship who narrates the story. A young man struggling to prove himself worthy of the command he was given a fortnight before the story begins, he finds Leggatt in the water, hides him in his cabin, and eventually helps him escape to freedom.
Leggatt The "secret sharer" of the Captain's cabin, Leggatt was the chief mate of the Sephora until he accidentally killed an insolent crewman during a particularly tense emergency during a storm. Stripped of his command and confined to his room until he could be brought to trial in London, Leggatt broke free from the Sephora's confines and swam to the Captain's ship, where he is discovered at the beginning of the story.
The Skipper of the Sephora A weak man bullied by both his crew and his wife, the Skipper of the Sephora visits the Captain's ship during his search for Leggatt. He is easily tricked by the Captain into believing that Leggatt drowned during his escape.
The Chief Mate A whiskered man whose "dominant trait was to take all things into earnest consideration," such as the scorpion he found in his inkwell a week before the beginning of the story.
The Second Mate Described by the Captain as a "silent young man, grave beyond his years," the second mate sneers at the Captain's questions about the Sephora early in the story. He embodies the undermining of the Captain's command that plagues the Captain until he meets Leggatt.
The Steward The cook on board the Captain's ship. At one point, he almost discovers Leggatt hidden in the Captain's cabin.