Cenote Zacatón

El Zacatón

Useful Information

Location: El Rancho Asufrosa, near Aldama. From Aldama follow Hwy 180 west, after 8 km turn right to Asufrosa.
Open: no restrictions.
Fee: free.
Classification: KarstCenote
Light: bring torch
Dimension: VR=339m
Guided tours:
Address: Cenote Zacatón.
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
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1795 written mention by Félix María Calleja, viceroy of New Spain.
1989 first recognized by a team of cave divers led by Jim Bowden.
APR-1990 entry and permission to dive granted by the owner, start of exploration.
1993 world record for women deep diving by Dr. Ann Kristovich, depth 168 m.
06-APR-1994 Sheck Exley died here during a try do set a new deep diving world record.
JUN-2007 explored by the NASA using the robot DepthX reaching the bottom of the sinkhole.


Zacatón is the most extraordinary of five cenotes which are actually part of the same cave system. It is sometimes said to be the deepest water-filled sinkhole in the world with a total depth of 335 m. Actually it is at the moment the second deepest known sinkhole with KarstPozzo del Merro in Italy being the deepest with a depth of 392 m. However, with ongoing scientific research this list of superlatives is often changing.

Zacatón is named after islands of zacate grass which grow in the cenote and are moving about with the wind. It is located on El Rancho Asufrosa, north of the small village Asufrosa. Here exists an enormous cave system with numerous openings to the surface. The most spectacular is obviously El Nacimiento Tamaulipas, a huge karst spring where the cave system drains into river Tamaulipas. Towards the north runs a chain of cenotes, waterfilled vertical shafts of the cave system, of which Cenote Poza Verde is probably the biggest. But not all of the cave system is flooded with water, there are the remains of a higher level which is above ground water level, called Caverna Los Cuarteles.

Although obviously long known to the locals, the locals did not know about the depth of this cenote. The cenotes were first discovered by a team of cave divers led by Jim Bowden in 1989. Its enormous dimensions were discovered during the subsequent exploration trips, several hundreds of dives in 1990 and 1991. In 1993 Dr. Ann Kristovich reached a depth of 168 m which was a world record for women deep diving. One year later, in 1994, Sheck Exley died while diving at this cenote. He and Jim Bowden were both trying to set a new deep diving world record. The actual record was 265 m, set by Sheck Exley some years before in the same cave system. He reached a depth of 276 m, which actually was a new record, where he died most likely from HPNS (High Pressure Neurological Syndrome). The news spread immediately and shocked the cave diving community, as Sheck Exley was known of being the best cave diver and most fanatic safety freak. He wrote the official cave diving safety handbooks for the NSS. Among these bad news it was almost forgotten that Jim Bowden set a new world record of 281.93 m at the same dive.

The cave system is extraordinary in many ways, beneath its size, the temperature of the water and its chemistry are rather strange. The warmest is Poza La Pilita with 34 °C, Zacatón and Poza Asufrosa have 31 °C, and Poza Caracol has 30 °C. Poza Verde is rather cool with 28 °C and is layered in thermoclines. It behaves similar to a lake, and less like a cenote, so it is probably not directly connected to the cave system. The water is also sulphuric, the sulfurous odor is obvious.

The sulfuric environment, the existance of nanobacteria and other extremophiles, and of course the depth made this well a good practicing ground for the NASA. They tested their robot DepthX here, which is intended to explore Europa, a moon of Jupiter, which has a wast ocean. Samples of microbes collected 115 m, 195 m and 270 m deep from water and rock walls revealed nine entirely new classes of microbes.

The temperature, the sulfuric milieu, and the deepest point some 130 m below the sea level make the development as a normal karst cave unlikely. It is considered a hypogenic cave. Sistema Zacatón has been formed by deep volcanic activity, groundwater is heated and turned slightly acidic by volcanic carbon dioxide and hydrogen sulfide.