"Better let me do it, Frank," said Jack.

"No; you're stronger than I am. You can hold this up better."

Jack did as his chum requested and a moment later Frank disappeared
under the wreckage, diving first to make sure that he got under.

Under the water the lad swam forward. His hand touched something that
was threshing about.

He felt sure it was the German. He rose. His head came in contact with
something, but the lad opened his eyes and saw that he was above the
surface. The imprisoned German was close beside him.

"Dive!" said Frank. "You can come out all right."

"Can't," was the reply. "My arm is caught."

Frank made a quick examination.

"I can loosen it," he said at last, "but I'll probably break the arm."

"Loosen it," said the German, quietly.

Frank took a firm hold on the arm at the elbow and gave a quick wrench.
He felt something give, and when he released his hold on the man's arm,
the latter sank suddenly.

Frank dived after him quickly. It was even as the lad feared. The