The unknown's knife was at that moment seriously incommoding a shark; his own had dropped, but he remembered it was attached by a lanyard to his belt. He recovered it; then, still retaining his hold of the other diver, he pulled himself down until he was able to slash the lashings that secured the leaden weights to the fellow's chest and shoulders. Then, and then only, did both men rise to the surface, Swaine horizontally, the other vertically owing to the fact that his feet were still weighted with lumps of lead. For the next hour, as far as Swaine was concerned, everything was a blank. He recovered consciousness to find himself lying on a mattress on the deck of the _Titania_. "How's the other bloke?" were his first words. "The other bloke," replied Villiers, "is progressing favourably in the circumstances." As a matter of fact, although the fellow's identity was revealed directly his helmet was removed, none of the others knew that a life-and-death duel was in progress when the shark butted in so opportunely. They were greatly surprised to find Swaine bob up unconscious from the bottom, still grasping the apparently lifeless form of his late antagonist--Siegfried Strauss. While Villiers and Beverley set to work to restore their comrade to consciousness, Harborough, O'Loghlin, and Trevear did a like office for the German. They were puzzled as to the cause of the loss of the man's hand, for the amputation had been performed as cleanly as if by a knife, while the pressure of his rubber wrist-band had checked what would have been a dangerous haemorrhage. Applying a tourniquet before cutting away the diving-dress, the three amateur surgeons felt that they had succeeded in saving the German's life unless he sank under the effect of shock to the system. Although curious to hear Swaine's version of the business, his comrades wisely forbore to question him until he had completely recovered from his narrow escape. Meanwhile they were putting forward numerous conjectures as to the reason for Strauss' submarine jaunt. "Where could he have come from?" asked Beverley. "The _Zug_ isn't anywhere in sight." "Unless she's off the other side of the island," added Villiers. "Even then he must have started from a much nearer base. We'll have to investigate." "Why did he?" persisted Beverley. "That's what I want to know." He received his answer in no uncertain way. A tremendous roar rent the sky, followed by a rush of air and the noise of cascades of water falling into the sea. Over the spot where lay the wreck of the _Fusi Yama_ the usually placid surface of the lagoon was lashed into a wide cauldron of leaping, hissing foam. "Fritz again--the dirty dog!" exclaimed Harborough, when the reverberations of the detonation had subsided. "It might have been worse if we had been working on the boat."