"Lay hold of this end here," he said to Jack. "If you can lift it a bit
I'll go under and have a look."
"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."