The safe has broken loose! And the cable that he and Harvey attached to it, though it’s damaged, is still intact. Someone must be hauling away on it up abovedecks because it is stubbornly and annoying taut. Right now the safe is caught up on jagged obstructions. Shaftoe has to pry it loose. The safe jerks onward and upward, drawn by the taut cable, until it gets caught in something else. Shaftoe follows the safe out of the cabin, up the passageway, up the conning tower ladder, and finally levers himself up out of the submarine and into the teeth of the storm, to a hearty cheer from the waiting sailors.