Interesting read. When I hear the word "sinkhole", the first thing that comes to my mind is cenote. Cenotes are fully or partially flooded sink holes and there are thousands of them here in Yucatan, Mexico. Some them look like this:
Amazing places to explore :)
Cenotes and their peaceful beauty seem very far from what I imagine what a sinkhole is haha -I have always thought of sinkholes as natural disasters.
Have you swum in any of these??!
Oh yeah, in many... They usually have also a very interesting and diverse wildlife so snorkeling is another great thing you can do in cenotes :) This one is my favorite, Cenote Yax Kin. Just outside of Tulum.