Harvey falls overboard in chapter 1 of Captains Courageous. At the beginning of the story, Harvey certainly is not the most seafaring of sorts. We can see that he is feeling seasick and certainly does not know how to comport himself properly aboard the ship. Having bragged that he never gets seasick, Harvey goes walking around the decks pretending to have proper sea legs beneath him. It is likely this overconfidence and bravado that leads him to be careless on board. Smoking the German sailor's potent cigar also adds to Harvey's feelings of unsteadiness.
Weak from seasickness Harvey leans against the ship's rail. It is there that "a low, gray mother wave swung out of the fog, tucked Harvey under one arm, so to speak, and pulled him off and away to leeward."
Harvey is swept overboard without a struggle, without crying out for help, and even without much of a thought. In many ways, Kipling likens this accident to a baptism in which Harvey emerges from the water reborn.