There was a snarl from the three men. Suddenly one dropped to his knees and seized Harris by the legs. Caught off his guard, the latter fell to the bottom of the boat and the others leaped on him. A knife flashed in the hand of one. With a cry, Jack stooped down quickly and seized the man's wrist even as the point of the weapon would have been buried in Harris' back. The lad twisted sharply and the knife went flying into the sea. "You would, would you!" cried Jack. He jerked the man to his feet, planted two hard blows on his chin, and as the man reeled forward clipped him once more. One, two, three backward steps the man took and then pitched over the side of the boat. "Two gone!" exclaimed Jack. But he was wrong. For the first man who had been knocked into the sea had been revived by the shock of the cold water. Swimming around the boat unobserved, he had come up behind Frank and now reached up and grabbed Frank by the coat. With a cry of alarm, the lad toppled into the water. Jack heard his friend's cry. Quickly he took in the situation. Harris had regained his feet and seemed capable of disposing of the two remaining Germans. With a cry to Harris, Jack leaped over the side. Some distance away he saw Frank struggling with the German who had pulled him from the boat and he swam quickly in that direction. "I'm coming, Frank!" he called. "Hang on to him." Frank was doing his best, but he had been taken by surprise and the advantage was with his opponent. The German's hand closed about the lad's throat and he was slowly choking him. Even as Jack came abreast of the struggling figures, Frank threw up his hands and the two disappeared from sight. Jack, greatly alarmed, dived after them. Below the surface of the water his hands encountered the struggling figures. He seized the first his hand came in contact with and struck upward. Upon the surface again, he found that he had seized hold of Frank. Keeping his fingers clenched tightly in Frank's coat--that the lad might not be drawn under again Jack aimed carefully at the face of the German, which now was close to him, and struck out with all his strength. Instantly, the hand on Frank's throat relaxed and the German sank from sight. By the force of the impact as the blow landed Jack knew that the German would trouble them no more. Supporting Frank with his left arm, he struck out for the boat with his right. The German officer leaned over the side and lent a hand in dragging Frank's limp body over the side. Jack clambered over after him. Then he took a view of the part of the boat where Harris battled with two of the enemy.