Cenotes, Playa del Carmen

This cenote is in Puerto Aventuras not far south of Playa and can be easily accessed by colectivo, see my tip re transport.
It's a beautiful crystal clear cenote, one part is open like a lake, the other is partly covered like a cave. The water is cool about 25' and very refreshing. It's a nice change from the beach, and usually there are very few people there.
Entrance fee is 40 pesos, there are bathrooms available.

Cenote/Cave/Cavern Diving
The area between Playa del Carmen and Tulum has some of the best cave/cavern diving in the world. Everyone should experience a "cenote" while visiting the Riviera Maya. If you are not a diver, I recommend a swim or a snorkle. Try Armando Elizalde of Scubacenote $85 USD for a double tank dive (lunch and equipment included). Best deal around and an excellent tour with an excellent guide.

There are hundreds of cenot'es you can swim in around the Playa Del Carmen Area. Some totally in a cove, some half exposed, some fully exposed. Lots of scuba divers LOVE cave diving. We went, on a recommendation to one called "the taj majal"
We should have guessed by the name, that it wasn't exactly that!
Ok, it was amazing, it was pretty, but what I love about the Caribbean is the warm water.
That doesn't happen in a cenote. Cold water, scuba divers who said it was amazing underwater where you could actually get down below and in parts you couldn't just swim into. They were using a light, for obvious reasons.
If anyone knows an amazing Cenote to swim in, please let me know, I'd like to see what the magic is all about!

A short walk across the highway from the Barcelo Resort brings you to Kantun Chi, a small park with 5 or 6 cenotes. Cenotes are sinkholes within the limestone and are very common on the Yucatan peninsula. For the admission price of around $8, you can wander around and even go in swimming or snorkelling in the cenotes. The water is extremely clear. Be sure to visit the (very) small Aztec ruins there as well.

At the end of the trail, there is a snack bar, as well as a souvenir 'booth' set up at the entrance. When we went, a young boy showed us a snake in a bucket, and offered to take it out for a few pesos. We declined, but still gave him the money.