I’ll say one thing, if I recall correctly, that the website of those guys at TIGHAR has lots of evidence that you may read and form your own opinions afterward. At least that’s what I did about a year and a half ago, lots of evidence and good links for more research, enough for me to have a good handle on what I believe are the facts. Tighar and others with their opinion of what happened to Fred and Amelia (that they flew to Nikumaroro) are way off base but they do show lots evidence for what happened that day and what happened at that point in the big attempt by Ms. E for an historic flight.
Without much better evidence, it would be illogical and irresponsible to conclude it isn’t a sinkhole with naturally-accumulated debris in it: That’s the least hypothesis, and nothing seems to refute it.
I think the flood shaft theory is false. There are some good websites out there that explain how they made salt for fishing using the trenches filled with fiber, etc. The one drain they did find, which would have to connect to the money pit to work, only went down 28 feet.
But that only reinforces how ingenious they were back then. I doubt many people today could come up with such an intricate system if they did not have some prior knowledge. Line the tidal flats with rocks and coconut husks and produce a never ending supply of concentrated salt solution? Humbug.