He continued to throw water at Sam and the youngest Rover tried to dodge. The raft began to rock, and of a sudden Sam lost his balance and went into the bay with a splash. Tom set up a laugh, for it was a comical sight, and it had been Sam's own fault that he went overboard. But then Tom's laughter came to an end as he saw the form of a shark moving swiftly toward the spot. "A shark! a shark!" he screamed. "Sam, get on board, quick! A shark is after you!" Sam had gone far down beneath the surface and he did not reappear at once. Then he came up spluttering. "Gosh! I didn't want a bath! Tom, you--" "Hurry and get aboard, Sam! A shark is after you!" Sam was about ten feet from the raft, and running to the spot nearest to him, Tom held out the end of his paddle. "A shark?" gasped the youngest Rover. "Yes! yes! Catch the end of the paddle!" Sam made a frantic effort to do so. In the meantime the shark came closer and Tom could see his enormous mouth and sharp teeth clearly. His blood turned to ice in his veins. Sam made a clutch at the paddle, missed it, and disappeared once more from sight. The shark rushed to the spot and turned in dismay, and driven to desperation, Tom hit the monster over the head with the paddle. Then the shark disappeared also. The next few seconds were full of agony for poor Tom. He gazed in all directions for Sam, and for the shark, but neither one nor the other was to be seen. "He must have caught Sam under the water!" he muttered. "Oh, Sam, what an awful death to die!" A slight noise at the upper end of the raft disturbed him. He turned swiftly, to see a wet hand glide over the woodwork. He made a leap and clutched the hand, and then Sam's head appeared. He gave a frantic yank, and both lay on the flooring of the raft. Sam was saved. "The shark!" gasped Tom, when he could speak. "Did it--it--bite you?" "No, but it grazed my shoulder," answered Sam. "If I had not dived down, I would have lost an arm at the very least." When they felt able they looked around, but the shark had disappeared. "That settles it," said Tom. "We must be careful and keep out of this water in the future. If we want to bathe, we will have to build a pool." During the remainder of the trip to the wreck both were careful not to run the slightest chance of falling overboard. "Not such a very lovely place to live in, after all," said Tom. "Snakes on land and sharks in the water, ugh!" And Sam agreed with him. Once on the wreck it was an easy thing to obtain the dishes and the knives, forks and spoons, and also some other things they thought they might require. They also brought away another gun, loading it up before leaving the ship. "Now, if Mr. Shark comes around again, we can give him a dose of buckshot," said' Tom. But the shark did not appear, excepting at a great distance. When Sam. told his story all congratulated him on his narrow escape.