For answer Jack arose in the boat. Quickly he threw off his coat and
kicked off his shoes. Then he poised himself on the edge of the boat.

"I'm going after him," he replied.

Before Frank could reply, he had dived head first into the sea.

With a cry of alarm, Frank also sprang to his feet and divested himself
of his coat and shoes.

"Stay close, men!" he commanded. "I'll lend a hand if it's needed."

He, too, leaped into the water.

Rapidly, Jack swam close to the wreckage. He continued to call to the
German, and while he received an answer each time, he could not locate
the man. Twice he swam around all that remained of the huge Zeppelin.
By this time Frank had come up with him.

"Can't you find him?" he asked.

"No," returned Jack, "and I am rather afraid to swim under there. The
balloon may sink and carry me under. But if I were certain in exactly
what spot the man is imprisoned, I'd have a try at it."

Frank listened attentively; and directly the German's voice came again.
To Frank it seemed that the voice came from directly ahead of him.

"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."