Portions of the following information were taken from www.cavediving.com.

Sistema Dos Ojos is not only one of the world’s largest underwater cave complexes, it also boast one of the largest and most beautiful cavern dives. Dos Ojos, which means “Two Eyes” in Spanish, is located just south of the X’el Ha ecopark. As you drive the bumpy dirt road back from the entrance, bear in mind that the original explorers of this system had to make this trip on foot, with their equipment hung on the back of burros.

The name Dos Ojos refers to two adjacent cenotes. Divers usually enter from the smaller of the two, known as the Eastern Eye. Two distinctly different types of cave dives are possible from this point.

One option is to go upstream, through the cavern zone, to the far end of the cavern tour line. You’ll know that you’ve reached your jumping off point when you see a plastic alligator with a Barbie doll in its mouth. Tie off here and continue upstream.

As you head into the cave, there are actually several different lines you can choose. These lines seem to change frequently — yet another reason why it is a good idea to use a guide for at least your first trip. One line will take you to the upstream portion of the cave, where you will see wide passageways and lots of formations. Yet another line will take you to Cenote Tak Be Ha, a huge, air-filled dome that can be artificially lit. This is a popular snorkeling site.

On your return, be sure to relax and enjoy the view as you swim through the immense cavern. It is simply unequalled.

The popular downstream dive is a traverse taking you past Cenotes Dos Palmas, High Voltage and Tapir’s End, and from which you will finally surface at Cenote Monolito (Monolith). A guide is essential, as taking the wrong line could be fatal. Because you will surface far from your starting point, you will need to arrange to have a vehicle waiting for you — or prepare for a long trip back.

Sistema Dos Ojos is immediately adjacent to Sistema Nahoch Na Chich. For a while, teams of explorers were competing to establish which was the larger cave. There was also a considerable effort to make a connection between the two (to date, no one has succeeded).