The Yucatán Peninsula, as a result, extended further out into the ocean than it does today.

What is now seafloor near the coast was dry land.

The cave systems that today extend beneath the peninsula and eventually under the ocean had a different water table position — lower, consistent with the lower sea levels — and much of the cave system was air-filled.

Hoyo Negro, at the time Naia died, was a dry pit within a larger dry cave system.

It was accessible, in principle, from the surface through whatever passages connected it to the outside — passages that are now flooded and that would have required a specific route through what must have been a dark and complex cave system even when it was dry.