Last lot I promise.
Mexico has some of the best cave diving in the world, The Cenotes. Translates into Sacred Well or Sacred Spring as this was the only source of fresh water for people who lived in this area thousands of years ago.
A complex network of tunnels that contains the oldest underwater stalagtite known on the universe (it takes 1 hundred years to grow one cubic centimeter).
There was some trippy stuff in the caves, fresh water sitting on top of salt water, producing what looked like a solid floor, (known as a haloclime) but you then drop through this false floor, the water goes blurry. The cave divers call this the tequila effect, and it is quite bizarre. Go under the false floor and then look back up, and you are diving under a mirrored ceiling, that is reflecting the floor below, not sure where you are then if you are going up or down. Very Trippy !!
The pictures are crap because there was nil light, black as black. But it may give you an idea....who knows!
http://community.webshots.com/slideshow?ID=551023205&key=GUlFrB