The reserve encompasses all the main ecosystems in the Central America and the Caribbean and its flora boasts 800 classified vegetable species. A total of 2,161 different animal species have been registered to date, including 339 types of birds, 103 mammal types. Reptiles in the area include the green, loggerhead and hawksbill sea turtles.
Its coast boasts 120 km of coral-reef barrier, which belongs to the second most important reef system in the world, the Great Mayan Reef. The fresh, clear waters offer an unparalleled coral formations 84 types of coral, more than 450 fish species and countless other life forms.
Within the boundaries of the Sian Ka'an Biosphere Reserve is Bocapaila on a 20-meter-wide peninsula, which then stretches for another 15 miles towards Punta Allen at Ascension Bay. This stretch of beach is a legally clothing optional beach.

There are five entrances to the reserve, located in Pulticub, Santa Teresa, Chumpon, Chunyaxche and Chac Mool. Guard parks, working by governmental organization SEMARNAT, are in each one of the entrances to make sure the fulfillment of the regulations within the reserve.

During the ice age, most of the underground cave systems dried up and the water that dripped through the porous limestone created the most extraordinary rock formations, which boast an incredible series of stalactites and stalagmites. When the underground rivers began flowing again, parts of the limestone vaults eroded, weakened and finally collapsed, unveiling a series of fresh water sinkholes. These were called "cenotes" by the ancient Maya, who considered them the entrance into the spiritual underworld.