It would appear that it has resisted recovery because there's probably nothing there.

A most clever ruse, to be sure.

To what end? Tremendous effort for no purpose but to intrigue? Kinda like building an enormous underground labyrinth then filling it with sand, just to get a giggle at how much people will do (long after you're dead) to find the presumed hidden treasure that isn't there.

It seems far more logical at this point that the Oak Island sinkhole is a result of natural phenomena and rumors / myths. I'm highly skeptical that there is anything at the bottom of the pit.

Probably just a lie. No effort.

There are layers of wood, etc, but they're probably just laid down by natural causes over the millennia instead of being a constructed building.

"layers of wood, etc" doesn't do justice to what is in place there: http://www.activemind.com/Mysterious/topics/oakisland/story....

Flagstones, layers of heavy timbers every 10 feet, a stone with carved glyphs at 90 feet, oak chests with coins, a sideways booby-trap well, Layers of blue clay at 130 and 160 feet, a cofferdam, and artifacts dating back 200+ years.

This strikes me as far, far more than an elaborate prank; it is a significant defense system meant to protect _something_

Or, the layers of timbers are trees felled in the same 100y storms, etc.

The flooding tunnel is likely just a normal geological feature, not some super-clever drift tunneling technique.

The stone is likely a fraud. Who would place a cryptic sign 90 feet down, telling themselves (in secret writing) to keep digging? Wouldn't they presumably know that they hadn't reached their treasure yet? Wouldn't they be more likely to place an innocuous sign on the surface, such as a gravestone? It's more likely a way to con investors out of further funds.

It's probably nothing but a rumor.