Dave wanted to go fishing, and after a good deal of trouble succeeded in making a hook of a big pin Bob had been using in place of a button on his jacket. For bait he used a big bug he found under a dead tree limb. "I don't know how this is going to work," he said. "Well, there is nothing like trying," answered the captain. "I'll see what I can do to bring down some more birds and find some fruit." Dave started to fish in the cove, and it was not long before he got a bite and pulled in a fish weighing a couple of pounds. This encouraged him, and inside of an hour he had a mess of nine to his credit. "We'll be able to get all the fish we want, that is sure," he reasoned. "Living on the island wouldn't be half bad, if it wasn't that those fellows on the _Raven_ may sail away and get at that treasure before we have a chance to reach the spot." Dave could not help thinking, too, of those on the _Swallow_, and he wondered how his father was faring. Having caught all the fish he wished he was presently joined by Captain Broadbeam, who had brought down two more birds. "I think I'll take a swim," said Dave. "I feel as if I needed the wash." "Very well, I'll sit on the shore and watch you," replied the captain. The young diver was soon in the water, which felt cool and refreshing. He loved to sport around, and dove and swam about to his heart's content. "Better come in," he said to the master of the _Swallow_. "Not to-day, lad," came back the answer. "How is the bottom where you are swimming?" "Sandy, with a few shells," answered Dave. "Do you know what I am thinking?" he went on. "There may be pearls here." "Perhaps." "I'm going to do some diving and take a look around." Dave was as good as his word and dove not once but a dozen times. He brought up a peck of oysters, but none containing pearls. "Must have been mistaken," he said. "I'll try it once again." He made a beautiful dive and reached the bottom with ease. But scarcely had he put out his hand for an oyster when he saw something that filled him with alarm. A long, dark object was moving along the ocean bottom towards him. At first he could not make out what it was, but presently discovered that it was a slimy water snake. The reptile was all of ten feet in length and five or six inches in thickness. Dave had no wish to encounter such a horrible-looking creature, and turning, he started to swim to the surface. The water snake came after him rapidly, and just as he got his head above water Dave felt something slippery curl itself around one of his legs and start to draw him under. CHAPTER XXI DAVE AND THE WATER SNAKE "Help me, Captain Broadbeam!" "What's the matter, Dave?" "A water snake has me by the leg." Before Dave could say more the water snake began to pull so fiercely that the head of the young diver was forced under the water. He struggled desperately, trying his best to get away.