This is a Cenote, or 'sinkhole'. The Yucatan does not have above ground rivers or lakes, they are all a network of underground artesian wells ... and are all interconnected by underground rivers. In spots all over the peninsula, the shale had collapsed, and formed these freshwater pools. The Mexican people swim in them (notice the stairs), and believe that they have healing powers. This one, divers went down to 300 feet ... and could not find the bottom. Some are deep into the ground like this, and others are level with the surface.

What? No pictures of you diving off?

Hey Slim, did you get to swim in the Cenote? That one looks very familiar with the steps running along the side. I was at one once where we got to jump off that platform at the top of the steps.

That water is soooooo refreshing after a hot day in the sun. I got to swim in on after a 100 degree day of touring Chichen Itza.

I love the Cancun/Cozumel area. The girlfriend and I vacation there every year.

Been to Cozumel twice......can barely remember either time! The cigar prices are ridiculous IMHO. Alas, the taxi rides after 5+ hours (I think that damn plastic Hammer did some damage as did the whistle blowing) at Carlos and Charlie's are worth the trip!
Water is absolutely beautiful.....Slim,I'm jealous.