“Is all this any of your business?”

“Not a bit,” admitted Jack Benson.  “All I’m here to do is to rescue you, or help in it.”

“Humph!” grunted the younger man.

“Heave a line, Hal!” shouted the submarine boy, signaling with one hand.  “Drive it straight.  I’ll get it.”

Swish!  Whirr—­rr!  It was a splendid cast.  As Jack leaped to his feet the slender rope fell over one shoulder.  Benson caught it with both hands.

“I’ll help you,” called the younger stranger with startling suddenness, reaching forward.  He grabbed at the submarine boy.  The next instant Jack Benson lost his footing on that wet, slippery sloop bottom.  He pitched, threw up his hands in an effort to regain his balance, then toppled, disappearing beneath the waves.

“They’re trying to drown Jack!” rang Hal Hastings’s excited voice.  “That was a deliberate trick!”

CHAPTER XIII

A HIGH-SEA MYSTERY

Splash!  Without a word as to his intentions Hal Hastings went overboard.  His head showed above the waves almost immediately, as he swam toward that other craft of mystery.

Jack Benson did not immediately reappear.  When he did come up, it was under the over turned hull.  He was obliged to make a half-dive in order to come out and up in the open.

By the time he did appear, his chum was close to him.

“Hurt?” hailed Hal.

“Not a bit,” responded Jack, after blowing out a mouthful of water.

“Then climb aboard with me, and see what these prize lunatics mean by their behavior,” requested Hal, not caring who heard him.

The sulky young man made no effort to oppose their boarding the hull.  Probably he feared to make too plain an opposition, with that dark-hulled, sombre, ugly-looking submarine torpedo boat lying so close at hand.

“Now, heave us a line, Eph!” hailed Hal.  The line came, and was caught.  Hal slipped over the further side with it, vanishing under water long enough to make it fast to one of the submerged cleats of the sloop’s rail.

“That will hold,” he reported, clambering back on to the bottom of the sloop.  “Now, sir,” turning to the older man, “since you have a life preserver on, you can easily get over to the submarine boat by holding to the line and pulling yourself along.”

“I’m afraid I can’t get across and keep my satchel,” whined the older man, nervously.

“I’ll take that and swim over with it,” proposed Hal, briskly, reaching out his hand for the bag.

“Oh, no, no!” protested the man.  “I’d sooner stay here.  The satchel doesn’t go out of my hands.”

“Better take to the water, father, and do the best you can,” advised the younger man in a growl.  “These fellows belong to the United States Navy, and they’re determined to rescue us.  Trust yourself to the water, and I’ll keep along with you.  These people will take us by force if we refuse any further.”