This a very nice experience. This exciting adventure tour starts with a ride in a 4×4 all-terrain vehicle that takes you to Rancho San Felipe, a small Maya family community where the Nohoch Nah Chich Cenote system is located (one of the longest explored underground river systems in the world).

Here you will take part in an unforgettable snorkeling adventure into the fresh waters of this underground river, swimming deep inside the caverns where you will observe stunning stalactite and stalagmite formations above and below this crystal-clear water.

You will then be transported to “Heavens Gate”, another entrance to this beautiful underground river system, for a relaxing swim in its refreshingly cool waters.

A traditional Maya lunch prepared by the women of this community then awaits you at the ranch. After lunch you will have the opportunity to visit the ranch and its inhabitants, a small Maya family that have lived in this remote jungle location for the last 30 years.

The expedition then takes you on a sea-kayak trip out to the reef system where you will snorkel and observe the spectacular corals, sponges and tropical fish of the Mexican Caribbean.

See it at http://www.cancuntravel.com/jungle-crossing.asp

The National Commission of Natural Protected Areas (CONANP) in Mexico, declared August 30th as the Whale Shark Day. Cancun recognizes and backs the efforts made by CONAMP in favor of the conservation of the whale shark as one of the privileged areas enjoying the presence of this fabulous creature.

The whale shark is the biggest fish in the world. It has a body that can reach sizes of even 18 meters. Its coloration is gray or dark blue on its back, with circular spots and light colored horizontal and vertical lines (white or yellowish) and a white belly. These patterns give the whale shark its local name: “domino.” In other areas, its appearance makes it known as “checkerboard”. Each individual displays a unique pattern which allows its identification, since it does not change with growth.
Unlike other sharks, its mouth is on the front end of its wide head and occupies the entire width of its body, facilitating plankton feeding. Its eyes are very small and are located on the lateral end of the head. The whale shark moves slowly near the water surface, since it filters great amounts of water to retain an ample variety of plankton and nekton, including small crustaceans like krill, crab larva and copepods, small fish like sardines, mackerel and occasionally prey of greater size like small tunas and squid. Phytoplankton and seaweeds could also be a part of its diet.

Source: Atlantic Whale Shark Project
http://www.conanp.gob.mx/tiburon_ballena.html

The majority of the Hidden World visitors describe this experience as the highlight of their trip to Mexico’s Yucatan peninsula. Hidden Worlds provides an authentic experience of the region’s awe-inspiring complex of caverns and cenotes that envelop one of the world’s longest underground waterways. These natural reservoirs were the lifeblood of the Mayan people for thousands of years.

Hidden Worlds Cenote Park is located in the heart of the Yucatan’s underwater cenote region, next to Riviera Maya and is offering the unique opportunity to experience Cenote Diving at its best. For Certified Open Water Divers, Hidden Worlds Cenote Park offers the world’s most incredible cavern dives.

Achieving worldwide-renown among scuba divers, Hidden Worlds has been rediscovered by nature lovers of all ages who come to observe its unique ecosystem via our environmentally-friendly Skycycle Canopy Ride, Jungle Zip-lines, Rappelling, Cavern Snorkel Adventures, and a Cenote Splashdown Zip-line while surrounded by the lush Mayan jungle. 
Come and experience the ecoadventure of your life !
http://www.cancuntravel.com/cavern-dive.asp