There was another scream. "Either got the other one, or the same one again," said Frank. They waited some moments in silence, but no further shots came from the foe. "By Jove!" said Jack, "you must have got them both. Let's go and have a look." Slowly, Frank started the hydroplane and they bore down on the enemy. Now they were two hundred, then one hundred yards away. "Must have got them, all right," said Frank. "I----" The flash of a revolver from the disabled craft interrupted him. It was closely followed by another and then two more. With a sudden move, Frank changed the course of the hydroplane. He felt a sharp pain in his left shoulder. "Got me," he called to Jack. The latter was alarmed. "Where?" he demanded. "Left shoulder," said Frank, quietly. "Nothing serious, though." Jack levelled his revolver and fired rapidly at the enemy. His pains were rewarded by howls of derision. "They tricked us, all right," said Jack, as he reloaded. "That's what they did. I should have known better, too. They almost settled us." "We've got to get them, some way," declared Jack. "Show me how, and I'll go along with you," declared Frank. "Well, I've got a scheme, but I don't know whether it will work or not." "Let's hear it." "All right. But first, can you manage this plane all right with that bad shoulder?" "Sure; it's not very bad." "All right then. Well, you keep under cover about here, moving about just enough to spoil the aim of the foe. I'll drop over the side and swim to the enemy. I can get there unobserved, all right, because they won't be expecting me. I'll pull one of them over and settle with him first. Then I'll get the other." "I don't know," Frank considered the plan. "I suppose it might work, but there is nothing sure about it." "There's nothing sure about anything," declared Jack. "But it's better than staying here all the rest of the night. Besides, we must hurry, you know." "That's right," agreed Frank. "All right, then. So be it. Will you take your gun?" "No use," said Jack. "It would be wet by the time I got there. Here I go." "Good luck," Frank called after him. Gently, Jack lowered himself over the side of the hydroplane, first divesting himself of his coat and shoes; then struck out for the disabled aeroplane. Slowly the lad swam, for he did not wish to betray his coming by the sound of a splash. The distance was not great and a powerful swimmer, such as Jack, could cover it easily in a few moments. Jack did not approach the enemy craft from the front. Giving it a wide berth, he swam around it and then, turning quickly, bore down upon the aeroplane more swiftly. He swam with his head barely above the water, and he was ready to dive immediately should he be sighted. There was not a sound aboard the aeroplane as Jack drew close to it. Raising his head slightly, he could see no human form. "Funny," the lad muttered to himself. "Wonder where they keep themselves. No wonder we couldn't hit them."