The useful art of self-defense is well taught at the Naval Academy, and Bill had ever been a proficient pupil. He jerked back his head, dodging the man’s fist by a hair’s breadth. Then as the other overbalanced, he stepped in with a short-arm jab to his opponent’s kidneys. This he followed up immediately with a powerful left hook to the point of the jaw, and the Herr Lieutenant went crashing overside, through the ropes of the gangway. There came the dull thud of his head as it struck the metal side of the submarine, and he disappeared down the narrow strip of water between the vessels. Immediately Bill dived after him.