The remains of dead animals, tossed into the bottom of a cave away from the light of day who-knows-how-long ago, have resurfaced in a most unexpected way.

Deep in the jungle outside Tulum, Mexico, divers, conservationists, and tourism leaders have combined forces to provide public access to this totally unique section of the world's second-longest underwater cave system. Under continual exploration since its 1987 discovery, the Dos Ojos underwater cave system extends for an estimated 51 miles, filled with crystalline, balmy freshwater accessible via 28 known sinkholes – locally called "cenotes" (say-NOH-tays). 

Throughout the course of these explorations, a team of divers came upon a truly marvelous discovery. Its jaw-dropping rock formations are punctuated by stalactites and stalagmites, with pockets of darkness in which blind cave fish flourish. Most staggering of all, the bottom of the pool has a soft, dune-like surface which, when sifted, revealed unforeseen treasures: the pit was littered with animal bones ranging from ancient to the more familiar, including the lower jawbone of a tapir and the fossilized remains of an extinct prehistoric camel.

Visitors to this site, which was nicknamed Pet Cemetery after these finds, with the proper credentials and training, can still see these skeletons and more, in their original positions. Scientists have pieced together a theory that the sinkhole was used as a disposal pit long ago, before the water table rose and flooded the animals' mass grave. As with all underwater caves, this location is not suited for beginning SCUBA divers, as cavern and cave diving requires specialized training. Fully guided dives are available for those who believe they have proper experience. Snorkeling, however, is an option at the site that allows visitors of all ages and abilities to enjoy the myriad speleothems in this highly decorated cenote. With respect for the fragility and unique nature of the Pet Cemetery Cenote, which is filled with delicate, low-hanging stalactites and other formations, it is requested that interested divers and snorkelers choose their participation method according to their skill level, so as to best preserve the wonder for generations to come. 

Above ground, on the jungle trek en route to the cenote, living ancestors of these animals are on full parade. Spider monkeys are a common sight in the trees above, not to mention more common ground-dwelling creatures of rainforest climes, all of whom prove as equally awe-inspiring to divers above water, as their deceased brethren at rest below the waterline.