LOL - I was actually being agreeable, not argumentative. It's you that seems bound and determined to argue.
I have another question now though, not related to your post.
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On land what usually happens is Timmy falls down the well (ok, mine shaft), Timmy's family sues everyone even remotely associated with the well, and someone along the way says, "don't want to go through that again," and fills the well with rocks. Does something similar happen with these under water caves? How many have been filled (covered with grates, whatever)?
If they don't get covered, what's the argument? After all, it seems like they are what's known as an Attractive Nuisance.