"But will he come up?" asked Frank.
"He's got to," was Ben's brief reply, "with that hook in him, he's as good as dead. He won't keep under much longer now."
"Hold up, Billy," shouted the boys to their imperiled companion, but the young reporter was too far gone and too choked with the water he had swallowed in trying to keep his head above water to reply.
Frank dived into the cabin and reappeared with a heavy rifle. He slipped into it a cartridge carrying an explosive bullet. Trembling with eagerness, he took up his position on the bow of the speeding Bolo, anxiously scanning the waters ahead for any sign of the shark's reappearance.
Suddenly an ugly black fin loomed up, cutting through the water like the conning tower of a submarine.
"Crack!"
The explosive bullet sped from the rifle, but either Frank's aim was bad from nervousness or the powder charge was too heavy, the ball struck the water fully a foot from the racing creature.
"Try again," said Ben consolingly, "I'll slow down the boat."
Luckily the shark had not dived and his fin still afforded a good mark. It was moving so rapidly, however, that it was going to be a difficult matter to hit the large body that moved beneath it.
Once more Frank rested the rifle and drew a careful sight on the fin. He aimed a little ahead of it this time, with the result that there was a terrific disturbance of the waters as the bullet sped home and the wounded creature convulsed with the pain.