"You may be killed," said Andy.
"And I may be killed staying here."
"If you go I shall go with you," returned the lieutenant.
Together the chums put on diving suits.
Then the torpedo trap was opened and they glided out on the bottom of the sea-cave.
It was of sand, with sharp rocks scattered here and there.
Oscar took with him a powerful electric hand light, and also a small dynamite shell.
The pair walked to the front end of the cave and made a thorough examination of the rocks.
"No way out of here," muttered Oscar, and then shook his head at Andy, who also replied in the negative.
The next movement was toward the rear end of the cave.