Cenotes are underground caves in fresh water, which so happens Mexico, particularly the Yucatan Peninsula has the most in the world. Since in that area there are really no lakes or rivers, the Mayans’ only source of fresh water was from these Cenotes. One will also notice the Mayan ancient cities/sites are very close to Cenotes, we know why.
This is my awesome tour guide, Jimmy, of Hidden Worlds Cenote Park I did a snorkeling tour of and it was incredible! They take you in a jungle buggy about a number of meters away until we arrive to the hole in the ground, taking a ladder down to the beautiful limestone cave and deep chilly waters. No photos unfortunately. It would have been a hassle to even bring an underwater one and be able to enjoy the sights. Plus it was one of those things that swimming around the sharp limestones hanging from atop and in the water too, being complex enough and not worry about taking photos. However one can hire the facility photographer. One thing, (or three things) which are mandatory to wear is a life jacket and head gear with an underground light attached and snorkel mask.
Jimmy was very nice and knowledgeable. The 2002 IMAX film, Journey into Amazing Caves features this cave. The park also offers zip lining in your choice of a jungle setting or cave. Of course the day I was there it was out of service.
Here are photos of this exploration. I did not take the photos myself (grabbed it from their Facebook page with permission) but this is the cave to go snorkeling at.
The other Cenote which is the one most people visit as it is included in virtually all of the Chichen Itza tours is below. The pictures are a little dull but with the darkness it is not very easy. As you can tell the water is absolutely freezing!