Most folks don't know that the only person who ever measured it says there is more than thirty feet of laha under the split, and a lot more than that elsewhere, up to 80 ft.
All other statements are being made by people who have never been in the cave or made any measurements.
Unless you count the guys who drive in pilings and think they have xray vision underground. My crew has driven in dozens of pilings, through soft layers and hard down to about twenty four feet max. The uneducated workers stood around talking about the cave as we drove them in, just like that day at the Split.

There is an old story about a building that fell in the cave about fifty years ago after it had fallen apart, down behind Oceanside. I talked to old Mr. marsh who loved that story. He was about 95 when he told me that he was one of those who slipped in that night and recycled the whole building and said it fell in the cave.