"Wait till it fills up and then swim out," suggested Larry.
"No, thanks," returned Dick. "We might be drowned by that operation."
The hole was irregular in shape, about ten feet in diameter and fully twenty feet deep. What had caused the sudden sinking was a mystery until it was solved by the water in the pool suddenly dropping away into another hole still deeper. Then of a sudden the trio went down again, this time at an angle, to find themselves in a good-sized cave, where all was dark and uncertain.
The tumble had wrenched Larry's ankle still more, and the youth could not suppress his groans of pain.
As soon as he was able Peterson leaped up, struck a match, and lit some brushwood which happened to be near and which the water had not yet touched.
By this light Larry's ankle was again attended to and bound up in a couple of handkerchiefs.
"If we keep on we'll get to the center of the earth," remarked Dick, as he gazed around curiously. "Where do you suppose we are now?"
"In one of the island caves," answered Peterson. "I told you the place was full of them. That's the reason the smugglers used to hold out here."
"Perhaps we'll come across some of their treasures."
At this Peterson shook his head. "Not likely. When the last of the smugglers was arrested the government detectives searched the island thoroughly and gathered in all to be found."