Bob dropped the lines in a heap and sprang to the pumps. For a moment
the two boys worked in silence, then Mart chuckled.

"Say, I guess we've got those pirates scared stiff, eh?"

"Looks like it," returned Bob, his eyes on the water. "That fellow
Birch--great Scott! Look there!"

The sudden fear in his voice struck Mart like a blow. Looking at the
water, he saw a little line of bubbles rising, and the terrible
significance of it sent horror into his heart.

"The hose is cut!" he cried, and leaped to the lines.

But though he tugged, there came no answering pull. White-faced and
stricken by the swift terror of what had happened, he began yanking at
the line and hose together, and as they came swiftly up he felt a thrill
of cold dread that seized on his heart and held him dumb.

With feverish haste he hauled in both lines, shrinking at thought of
what had befallen the old quartermaster. Then, without warning, the
lines shot up and curled about the landing--cut short and clean.

"The shark--" began Bob, white-lipped and paralyzed with horror.

"No!" exclaimed Mart, his mind leaping ahead swiftly. "The kris, Holly!
He said it was stickin' in the wreck. The lines came against it and cut
off! Here, get the other lines connected up with that spare helmet--move
lively!"

Bob stumbled forward in blind obedience, as Mart flung away the useless
lines and darted to the spare diving suit, which lay ready with its hose
and lines coiled at its side. He opened the wide neck and, snatching off
his shoes, began to get into the huge garment in feverish haste.

"What you going to do?" queried the doubly horrified Bob.

"Goin' down, o' course," snapped Mart. "Hurry up, there!"

CHAPTER XV

MART GOES DOWN

"But, Mart!" Poor Bob's voice rang out in terror-stricken accents.
"Jerry'll be drowned before you can reach him!"

"Shut up!" crackled out Mart, snapping his wrist-bands close. "He won't
either. When the air hose is cut, that helmet valve closes
automatically. Jerry's down there, an' he can't get up, that's all.
Hurry up with that hose!"

Bob fell to work again, his fingers trembling. Mart got into the big
shoes and laced over the flaps, for he knew that every second counted,
but at the same time he must overlook no slightest item in his dress.

Never had his mind worked so swiftly as now, when the danger call came.
It had occurred to him to drop over a weighted line, but he knew that
Jerry might be unable