"I'm not so sure about that," declared Frank. "Well, I am," said Harris. "The German sailor is all right. It's the German officer who makes all the trouble. They'll help us if they can." The three swimmers were a short distance from the ship now. Jack raised his voice in a shout. "Help!" he cried in German. There was no move aboard the German vessel to indicate that the lad's cry had been heard. "Told you so," said Frank. "Don't cry too soon, youngster," said Harris. "We'll try it again, and all yell together." They did and this time their cries were heard. Several men aboard the German vessel stopped their rushing about and gazed across the sea in the direction of the swimmers. One man produced a glass and levelled it in their direction. Then he turned to the others and they could be seen to gesticulate excitedly. "One wants to save us and the others don't," declared Frank. For some moments the men continued to argue. One shook his finger in the faces of the others and pointed in the direction of the swimmers. "You're all right," declared Frank, speaking of the one man. "Wish I were there to lend you a hand. But I'm afraid the others are too much for you." At this juncture the man who opposed the others produced a revolver and made an angry gesture. He was ordering the others to the aid of the three friends in the water. "By Jove!" said Harris. "He's all right. I'd like to be able to do him a good turn." And the chance was to come sooner than he expected. Apparently the men aboard the German vessel had decided to obey the order of the man who would save the three swimmers. A boat was lowered over the side. Three men stood ready to leap into it. The hopes of the three friends in the water rose high; but they were shattered a moment later in a sudden and unexpected manner. A dull rumbling roar came suddenly across the water. Instantly all became confusion aboard the German vessel. Officers shouted hoarse commands and struck out with the flat of their swords as members of the crew rushed for the rails. "An explosion!" cried Frank. "Swim back quickly." The others understood the significance of that strange rumbling aboard the German vessel as quickly as Frank, and turning rapidly, they struck out as fast as they could. An explosion such as that dull roar indicated could have but one result and the lads knew it. Evidently there had been a fire on board--that accounted for the strange activities of the men on the ship--and the flames had reached the vessel's magazine. A second and a louder roar came now. Men jumped into the sea by the scores and struck out vigorously that they might not be pulled under by the suction when the ship sank. Then there came an explosion even louder than the rest. The great ship parted in the middle as though cut by a knife. A huge tongue of flame shot high in the air. Hoarse cries from aboard, screams and frightful yells. Split in twain, the vessel settled fore and aft.