ossible--

"Ah!"

A little click behind his ear, and the noise of pumps stopped. A flicker
of the dim gray shape above, then it became larger, more firm of
outline. Down through the water curled the air hose and lifeline, bitten
through, and Mart had a vision of the tremendous fish as it flitted past
overhead, turning in a great curve. The sight was paralyzing. Then Mart
gripped the kris, tore it from the barnacled wood, and whipped around to
meet his enemy. He had no way of getting up to the surface, his
air-supply was limited--but he would not give up without a struggle.

CHAPTER XVI

THE BATTLE

When he gained a full and nearer sight of the Pirate Shark, Mart's
courage all but failed him. For a moment the gigantic fish seemed to
hang poised in the water above and beyond him, some twenty feet away;
what its actual size was Mart could not guess, in the dim and blurred
light, but there could never be another such shark as this in all the
oceans!

Huge, cruel-eyed, with its mouth showing as he looked up at it, Mart
never forgot the horror that seized him at his first face-to-face
meeting with the Pirate Shark. He thought of a thousand things in that
one moment--the uncanny cunning of the terrible fish in first cutting
him off from all help by biting through his lines, poor Bob waiting up
above in agonies of suspense, and above all, the awful fact that unless
he conquered quickly, he would suffocate.

Still the shark hung poised above him, the immense body motionless
except for the gently-waving fins and tail. The big dorsal fin was
hidden from him, so he could not see whether it had been pierced by the
bullet or not. But he must act, and act quickly! What should he do?

In order to get at the monster shark with the kris, he would have to
expose himself. If the brute was cunning enough to cut his lines, he
would be too wise to attempt an attack while Mart stood in the
wedge-shaped opening of the wreck. There, he could not reach the boy,
and would realize it.

Mart wasted no time in hesitation. He was running a terrible risk, for
once the shark butted into him or struck him with its tail, he would be
flung off his balance and would be lost. But remembering his great
lightness in the water, remembering how easily he could leap out of
danger, he stepped forward confidently from his shelter, the kris held
ready.

No sooner had he done so than the shark began to move. Gradually, with a
terrible slowness,