He was treading water, holding to a rope that dangled over the side of the ship when, with no interior tremor of warning, a cut that he almost thought had penetrated to the bone lashed across his shoulders narrowly missing his left ear. Without stopping to think Chris took half a breath and submerged as deeply as he could go, hearing above him, even through the sounds of the battle and the wavering water, the "fleck!" of Claggett Chew's metal-tipped whip as it hit the water where he had been only a second before. Chris would have dived under the great barnacled hull of the _Vulture_ then and there, to come up on the other side, but good swimmer though he was, he was unsure that he could hold even a full breath for so long a dive. Added to this, he had had no time to do more than gasp a momentary breath of air, and even as he rose to the surface with bursting lungs, he saw the figure of a man leap into the water from the side of the _Vulture_. Before the bubbles of the man's descent had had time to disappear, the most dreaded of all sights for a swimmer showed itself above the water. It was the sinister triangle of a shark's-fin cutting the surface of the sea as it advanced with terrifying speed to where Chris gazed, almost paralyzed with horror. Thrusting the knife into the pouch at his neck, Chris took the shape of a dolphin and plunged deeply, even as the infuriated shark was carried over and beyond him by its own impetus before it could turn. But turn it did, with lightning speed, and Chris knew he had no protection against that murderous underslung jaw racked above and below with deadly teeth. The shark, in one long powerful movement, had turned and gone under the dolphin, which now raced upward from the dim, lightless depths of the sea to the surface where it hoped to escape. The shark turned on its back with a motion at once lazy and sickening in its assurance of its prey. Its soft greenish-white belly glimmered slimily in the sea, its frightful jaws open as it came almost languidly up through the water, certain of snapping its adversary in half. But in that one moment when it turned belly uppermost, its eyes were unable to watch its goal, and in that moment the dolphin made a desperate leap from the water and a sea bird soared into the air. The sea bird had no more than wheeled to sight the shark below, when a scream from the air above it made it instantly drop and shift to one side as a hawk, talons spread and eyes red with hatred, plunged down from a great height, its beak open to seize and to rend. The sea bird, veering away on the wind, became a fly, but the hawk instantly vanished to be replaced by a bat, which darted after the fly with such velocity that it was the current of air from its wings that drove the fly closer to the pirate ship. [Illustration]