ut his
last chance and it won't be so easy to drive him off this time."

Around and around the two swimmers the shark circled. He moved with
amazing rapidity, and it seemed as if the two hard-pressed and tired
swimmers must become dizzy if they followed his every move.

"He'll fly around them like that," said Grant, "until he sees a good
chance and then you'll see him strike like lightning."

"They mustn't give him a chance," muttered Fred doggedly.

"They won't if they can help it, you may be sure of that."

"There he goes!" cried Fred. "No, not yet," he corrected himself.

"He'll strike, all right. Just watch him."

"If Sam can only use that knife."

"Maybe he won't attack Sam."

"They're awfully close together now," said Fred. "If he goes for John,
Sam can stick him and if he goes for Sam, why he has the knife right
there."

"The old knife will never go through that shark's hide," exclaimed
Grant. "It's almost as hard as sheet steel."

"Here's the test anyway," cried Fred, and as he spoke the giant fin
could be seen darting suddenly towards the two swimmers. Just before it
reached them it disappeared beneath the surface of the water.

"He has turned bottom side up to bite," muttered Grant, fully
understanding just what was taking place.

Sam and John had noted the approach of their enemy and both realized
that the crisis of the whole affair was now at hand. If they could elude
him this once, the chances were that they could reach shallow water
where the shark would not dare to follow them. They both began to kick
violently and splash as much as possible with their hands; they shouted
and yelled; they did everything which they thought might possibly aid
them in scaring the great ugly fish away.

Grant and Fred on the shore held their breath while all this was taking
place and their hearts almost stopped beating. With feverish anxiety
they awaited the result of the battle taking place before their very
eyes.

"There's John," cried Grant suddenly. "Where's Sam?"

"I don't see him. I don't see the shark either."

"The splashing has stopped. Sam must have been killed."

"Oh, no," exclaimed Fred. "Don't say that. It can't be."

"Where is he then?"

"Look!" cried Fred.

The water some five or ten yards behind John was suddenly churned into
froth. Red, bloody froth it was and evidently some gigantic struggle was
going on. All at once, just on the outside of the miniature maelstrom,
appeared a small