Connect with us


Diving Beyond 250 Meters: The Deepest Cave Dives Today Compared to the Nineties

How deep are the deepest cave dives today, compared to those three decades ago when technical diving was just getting started? InDepth editor-in-chief Michael Menduno and deep diving pioneer Nuno Gomes team up to review the history of deep cave diving, discuss the issues involved, and identify the people who are pushing our underwater envelope.



By Michael Menduno and Nuno Gomes 

Header photo showing Nuno Gomes during his 1996 record deep cave dive at Bushmansgat. Photo by Theo van Eeden

A little more than a year ago, we ran an InDepth article, “Extending The Envelope Revisited: The 30 Deepest Tech Shipwreck Dives,” which compared the deepest tech shipwreck dives as of 2020 with those conducted in the 1990s when mixed gas technology was just emerging. Not surprisingly the story drew a lot of reader attention. As a result, it seemed fitting that we publish a similar article examining deep cave diving. Accordingly, I teamed up with deep diving pioneer and Guinness world record holder Nuno Gomes, who had already completed much of the needed research for his 2016 book that he co-authored with Olo Sawa, Beyond Blue: Journey Into the Deep.

Since the 1990s, technical divers have explored considerably deeper in caves than they have on shipwreck exploration dives, which is not surprising. The cave environment is far more conducive to staging equipment such as gas and scooters required for deep dives, conditions are also far more stable and rarely subject to weather compared to open water dives, and caves may also offer more psychological comfort for divers, for example, there is less sense of depth then a vertical plunge in open waters.

Sheck Exley with Nuno Gomes at Bushmansgat 1993

In addition, with the possible exception of Jacques Cousteau, cave divers were arguably the original tekkies and worked out many of the initial fundamentals of tech diving in terms of equipment and protocols. Again, likely due to the environment, they were also the first amateur diving community to begin experimenting with mix technology. In 1967, South African British Sub Aqua Club (BSAC) divers Roly Nyman [Gomes’ original cave instructor], Ian Robertson, John van der Walt and Danny van der Walt conducted the first trimix (an oxygen, helium, nitrogen mix) dive by cave divers to 107 m/350 ft in Silent Pool, in Sinoia, Rhodesia. After some unsuccessful attempts during the seventies, in 1979 Dale Sweet dived to 110 m/360 ft at Diepolder II in Florida, marking the first successful use of trimix by sport divers in the US. 

Swiss diver Jochen Hasenmayer was soon to follow in 1981 with a trimix dive to 145 m/476 ft at Fountain of Vaucluse, France, using modified tables from pioneering commercial diving Oceaneering. This was the first of a series of ever deeper dives conducted by Hasenmayer, which inspired cave explorer Sheck Exley to begin his record-setting, deep mix dives. 

Others, like cave explorer Bill Stone with his Wakulla Springs 1987 Project, as well Parker Turner, Bill Gavin, Lamar English, and Bill Main, who went on to form the Woodville Karst Plains Project (WKPP), began conducting mix exploration dives with the help of decompression physiologist Dr. Bill Hamilton. Similarly, in Europe, divers such as cave diving and rebreather pioneer Olivier Isler, as well as Stuart Clough, owner of Carmellan Research, who worked with British tech diver Rob Palmer, also embraced the new deep diving technology.

Nuno Gomes and Jim Bowden diving the Lost Blue Hole in the Bahamas

In contrast, the US wreck diving community didn’t begin to adopt mixed gas diving in earnest until the early 1990s, with help from tech diving pioneer Capt. Billy Deans, owner of Key West Diver, Key West, Florida—the first tech training center in the world. In fact, most wreck divers didn’t even use oxygen for decompression until the late 1980s; again, Deans was instrumental in helping the Northeast wreck diving community develop safer decompression protocols

The View from aquaCORPS Circa 1993

In December 1993, my magazine aquaCORPS published reports from Sheck Exley, and Jim Bowden under the header “DEEP UNDERGROUND,” along with a table and explanation provided by Exley titled, “Comparison of Sub-500 foot (150 m+) Technical Dives,” that listed 13 known dives to depths beyond 150 meters. That table is shown below. All of the dives were cave dives conducted in fresh water with the exception of Jim King’s dive to 209 m/683 ft at Dean’s Blue Hole in the Bahamas. Note that the listing, JB’s 170 Fathom, as it was initially called, was Zacatón, in Tamaulipas, Mexico, where Exley died in 1994. 

From Sheck Exley: This table summarizes the 13 self-contained technical dives that have been successfully conducted to date beyond 500 feet (154 msw). All of these are cave dives, though the open water community is not too far behind. All dives except King’s Blue Hole descent were conducted in fresh water. No DCI symptoms were reported other than general fatigue-not surprising alter such long dive times, and a single case of skin bends. HPNS was reported on two of the dives, both at Bushmansgat, South Africa: Gomes’ 1992 descent to 500 flw/163 msw, and Exley’s recent descent to 863 ffw/257 msw. Reports of HPNS will probably increase as the technical diving community makes more helium dives to depths below 400 feet/123 metres due to the rapid descent rates. The water temperature for the dives varied considerably. The coldest by far was Vaucluse, 55 degrees F. (l3°C ). Next is Bushmansgat, at 66 degrees F (19° C), followed by Mante at 78 degrees F (26°C). The warmest dive was Bowden’s 170 Fathom Grotto, at a very pleasant 87 degrees F (31C° ). *Note that the bottom mix on these dives were blended by topping a fixed amount of helium with air, a convenient field mixing practice for remote locations.
Sheck Exley after his 721 ft/221 m dive at Mante in April, 1993
Dr. Ann Kristovich was the only woman to make the list with her (woman’s) record deep dive to 170 m/554ft at Zacatón. 

Note that the dives were dominated by Exley, and to a lesser extent Nuno Gomes and Jim Bowden. Not listed are likely some further dives by Hasenmayer including his 1989 dive at Lake Wolfgang, Austria, where he suffered decompression illness and was paralyzed. Note also that Bowden’s partner Dr. Ann Kristovich made the list with her (woman’s) record deep dive to 170 m/554ft at Zacatón. 

Decompression schedules for these dives were calculated using modified Oceaneering Tables, Hamilton’s Diving Computational Analysis Program, (DCAP), and Exley’s software program Dr. X. The table also includes some discussion of the first reported cases of High Pressure Nervous Syndrome (HPNS) by sport divers, in this case Exley and Gomes.

Bowden’s Deep Diving Chronology Circa 1998

In 1998, Bowden, who had conducted the deepest cave dive to 282 m/925ft at Zacatón in 1994, which was later surpassed by Gomes in 1996, compiled a chronological list of 38 sub-150 meter dives conducted from 1982-1998. Along with the table, Bowden wrote a short (unpublished) essay detailing his experience and views on deep diving, DCS, HPNS, depth calculations. We titled it, “Thoughts on Diving To Great Depths.” Bowden’s list is shown below.

Olivier Isler with his triply redundant RI-2000 semi-closed rebreather circa 1993

All but six of the dives detailed in Bowden’s list were cave dives: there were five lake dives (one on the wreck of the Edmund Fitzgerald in Lake Superior, Michigan), and one dive in the Mediterranean Sea. In addition to Exley, Gomes, and Bowden, some of the new names that appeared on this list and subsequent lists as shown below are Pascal Bernabe, Olivier Isler, and Gilberto Menezes de Oliveira. Again, Kristovich remains the only woman to make the list. 

Note that by 1998 several new decompression programs had gained favor by the faithful including British tech pioneer/engineer Kevin Gurr’s ProPlanner, a decompression model by French commercial decompression engineer JP Imbert turned tech diver, and the Abyss software model marketed by Chris Parrett and Joel Silverstein. 

The Darkness Continues to Beckon Circa 2000

In 2000, British cave diving pioneer and author Martyn Farr published a list of the 14 deepest cave exploration dives beyond 150 m/489 ft. His seminal book, The Darkness Beckons, first published in 1980, and subsequently updated in 1991 and 2017, details the history of cave diving beginning with the early British dives at Wookey Hole. Farr’s list is shown below.

All but one of the divers can be seen on previous lists, and all of them are men. Note that five of the 14 dives were conducted by Brazilian cave explorer de Oliveira, while Bernabe claimed two of the deepest dives. 

The Deepest Cave Exploration Dives Today

Brazilian explorer Gilberto Menezes de Oliveira.

In 2016, Gomes published a list of deep dives in his book, Beyond Blue. He updated and refined the list for this article to focus on the 13 deepest cave dives, all beyond 250 m/816 ft—the new demarcation for über-deep cave dives vs. sub-150 meter dives in the 1990s. Seven of these 13 dives were conducted after the year 1999. 

French explorer Pascal Bernabe

Note that obtaining an accurate measure of extreme depths can be challenging, especially in the cave environment, depending on the topography; divers sometimes have to rely on estimates. Few gauges are rated deeper than 200-250 meters, and even then, pressure sensors are not usually calibrated to read accurately at those depths. Gomes used an imperial Parkway gauge that went to 999 feet and then started counting again from zero. In practice today, depths are calculated using a combination of gauges, ropes, sonar, trigonometry and ROVs. 

Gomes’ table is shown here and lists the dives by their nominal depth, but includes a column for altitude adjusted depth. Note that Bushmansgat is located 1550 m/5000 feet above sea level. When adjusted for altitude, Gomes’ dive was equivalent to a sea level dive to a depth of 339m/1,112 ft making it the deepest cave dive on record.

It should also be noted that all of the dives shown on Gomes’ table were solo dives (though there were support divers at shallower depths). Gomes believes that’s the only way these dives can be conducted. “It’s safer,” he explained to me. “If something goes wrong, only one diver dies instead of two.” The problem according to Gomes is that it’s not possible to save someone at these depths in the event of trouble. “You are pushing so close to the physiological envelope that you can hardly save yourself let alone someone else, if something goes wrong. You don’t have the time or the capacity, you have to concentrate on yourself,” he said.

New to the deepest cave diving list are French cave explorer and former military and commercial diver Xavier Méniscus, and Polish cave explorer Krzysztof (Kris) Starnawski. Insiders say there is a healthy competition between the two über-divers reminiscent of the rivalry between Exley and Hasenmayer back in the day. Watch this space. 

Nuno Gomes and Polish cave explorer Krzysztof (Kris) Starnawski.

Interestingly, Miniscus, Gomes, Exley, Bowden and Starnawski each account for two of the deepest cave dives, while the others on the list claim a single entry. All of the divers are still alive with the exception of Exley and David Shaw who both died conducting extreme deep dives. Spanish cave explorer Jordi Yherla Santaolalla, suffered decompression illness at deep depth during ascent from his 253 m/830 ft dive at Font de Estramar, France in 2014. He was aided to the surface by his support team and was treated for DCI.

Spanish cave explorer Jordi Yherla Santaolalla

It’s also interesting to note that in addition to claiming the deepest cave dive, Gomes set the Guinness World Record for the deepest (open water) scuba dive of 318 m/1,044 ft near Dahab in the Red Sea in 2005. Several weeks later, Pascal Bernabe claimed he set an unofficial record to 330 m/1077 ft in Corsica. Their records were supposedly bested almost a decade later by Egyptian ex-military diver Ahmed Gabr in 2014 with his reported dive to 332.35 m/1,090 ft in the Red Sea which earned him a Guinness World Record

French cave explorer and former military and commercial diver Xavier Méniscus.

However, Gabr’s record remains under a cloud of doubt in the tech diving community, as evidence that suggested that he did not actually make a record dive surfaced last summer. In February of this year, Guinness announced they had investigated claims that Gabr faked his record dive, and said they found “no conclusive evidence which establishes foul play.” However, it did not address specific allegations, nor did they interview Gabr’s support team.

Not shown on Gomes’ list are the recent remarkable deep exploration dives conducted by Australia’s Wet Mules led by Dr. Richard “Harry” Harris, and Craig Challen in Pierce Resurgence. In early 2020, Harris and Chalen pushed the cave to the amazing depths of 243 m/792 feet, which fell just shy of the 250 meter cutoff. Note that Harris and Chalem dived as a team vs as solo divers. I’m sure the discussion of diving solo vs. as a team will continue as cave divers dive deeper. And we will.

Comparing Today’s Deepest Dives to The 1990s

Diving equipment has significantly improved since the 1990s, and rebreathers have become the tool of choice for deep diving, as the ever prescient Stone and Isler predicted. Six of the seven deepest cave dives conducted since 1999 were done on rebreathers; all of the 1980-1990s dives were done on open circuit.

There have been no major changes in decompression algorithms short of adding conservative factors and adapting the algorithms for constant PO2 rebreather diving.

However, Gomes pointed out that divers are breathing mixtures with far greater helium content consistent with the new research on gas density and diving safety. In addition, more attention is being paid to transitioning gases from helium to nitrogen during the ascent to avoid isobaric counterdiffusion

Verna van Schaik, dived to 221 m/721 feet, at Bushmansgat in October 2004

Note as of yet, no women have made the deepest dive list. Currently, Vera van Schaik, holds the Guinness World Record for the deepest scuba dive (women) to 221 m/721 feet, which she made in October 2004 at Bushmansgat, surpassing Kristovich’s record of 169 m/554 ft. Van Schaik went on to write a book, Fatally Flawed: The Quest to be Deepest, about her experience, and also wrote the forward to Gomes’ book. 

Since Van Schaik’s dive at Bushmansgat, two female divers have died trying to break her record. Forty-year old French diver Brigitte Lenoir died in Dahab, Red Sea, in May 2010. Then in September 2017, 45-year old Bulgarian technical diving instructor trainer, Teodora Balabanova, died attempting a dive to 231 m/754 ft, while her husband, Mihail Balabanov, who had accompanied her, was injured. 

Today, as this article is being written, one of Gomes’ students, Karen Van Den Oever is planning to dive beyond 250 m/816 ft at Bushmansgat on March 25, 2021. If she does go through with it, we plan to announce the results in the issue. [See: “South African Cave Diver Karen van den Oever Sets New Women’s Deep Cave Diving Record.”

Cave Divers Do It Deeper

How do the deepest cave exploration dives compare to those of shipwreck divers? The ten deepest cave dives today average 284 m/926 ft (adjusting for altitude and freshwater), compared to an average depth of 209 m/682 ft for the ten deepest cave dives in 2000, or approximately 75 m/245 ft deeper. 

In contrast, the ten deepest shipwreck dives today average 176 m/576 ft, compared to 121 m/398 ft for the ten deepest shipwreck dives in the 1990s (see Extending The Envelope Revisited: The 30 Deepest Tech Shipwreck Dives). In other words, the deepest cave dives exceed the deepest wreck dives by 108 m/352 ft on average, and as a result of depth and geography are also likely considerably longer on average. 

The ten deepest cave dives today average 284 m/926 ft (adjusting for altitude and freshwater), compared to an average depth of 209 m/682 ft for the ten deepest cave dives in 2000, or approximately 75 m/245 ft deeper. In contrast, the ten deepest shipwreck dives today average 176 m/576 ft, compared to 121 m/398 ft for the ten deepest shipwreck dives in the 1990s.

Will cave divers continue to push depths ever deeper over the next twenty years as they did with the last? “Xavier and Kris may push the limits a little deeper. Who knows,” Gomes told me. “However the work of breathing (WOB) becomes a problem at those depths, particularly on rebreathers.” [Note that Dave Shaw died of respiratory insufficiency at a sub-250 m dive at Bushmansgat—see video below] 

Will cave divers take a lesson from the cutting edge of commercial diving and adapt hydrogen as a breathing gas for extreme depths? Hydrogen is half the weight of helium, and its slight narcotic properties have been shown to ameliorate the effects of HPNS, which is believed to be a contributing factor in Exley’s death. In fact, ambitious tech divers have already conducted an experimental hydrogen dive according to retired scientific diver of the US Navy Experimental Diving Unit (NEDU) John Clarke’s latest blog, “Hydrogen Diving: The Good, The Bad, The Ugly.” Interestingly enough, Sheck mentioned the use of hydrogen and hydreliox towards the end of my 1992 aquaCORPS interview with him, “Exley on Mix.”

It’s also likely that future tech divers may one day have access to lightweight, self-contained one-atmosphere exosuits, similar to what atmospheric-diving-systems (ADS) pioneer Phil Nuytten, of Nuytco Research, is building for the US Navy. Far-fetched? In 2014, British caveman Phil Short piloted an exosuit on a Woods Hole expedition in Greece to depths of 123 m/400 ft in search of the Antikythera Mechanism. It’s not hard to imagine.

I asked Sheck, a few years after his record 264 m/867 ft dive at Mante, what he thought the ultimate depth limit would be. “There is no limit,” he said. “We’ll always find a way to go deeper and deeper. That’s been the pattern all along. Ten years from now, twenty years from now, people will be doing things we’ve never dreamed of, and I see no reason for that to change.”

 “There is no limit,” he said. “We’ll always find a way to go deeper and deeper. That’s been the pattern all along. Ten years from now, twenty years from now, people will be doing things we’ve never dreamed of, and I see no reason for that to change.”

Additional Resources:  

 What does it take physiologically to dive beyond 250 meters? Here in this story from aquaCORPS #11 Underground XPLORERS, August 1995, we analyze extraordinary number of factors must be considered to conduct a 1000 ft/307m dive and includes Bowden’s decompression table. See: Absolutely Risky Business

 By comparison, here is Nuno Gomes’ decompression table used for his record 1996 dive to 282.6m/927 ft.

 What was Bowden’s motivation to bottom out Zacatón? Also in aquaCORPS #11 Underground XPLORERS, we interviewed Jim Bowden about his plan to get to the bottom of Zacatón: “I want to see the end of the cave. This one just happens to be vertical.”

You can find out more about Nuno Gome’s diving projects including his record dives on his website.

For the deepest shipwreck dives see: Extending The Envelope Revisited: The 30 Deepest Tech Shipwreck Dives

Video Resources: Deepest Cave Dives 

World Record Cave Dive -286.2m (939 feet) 30-déc-2019 – Xavier Meniscus at Font Estramar

World Record Cave Dive – 282.6 m (927 feet) – Nuno Gomes

Hranicka Propast 265m-Kris Starnawski

Récord de profundidad de Europa en espeleobuceo-Jordi Yherla Santolalla

Pearse Resurgence 2020-Richard Harris and Craig Challen

Diver Records Doom | Last Moments-Dave Shaw

 Olivier Isler : la Doux de Coly

Dean’s Blue Hole Cave Exploration by the Bahamas Caves Research Foundation 2019-Jim King

Sheck Exley Bushmansgat Cave Part 1

Sheck Exley Bushmansgat Cave Part 2


3D maps produced by DEPTHX of the Zacatón Cenote System by Stone Aerospace

Nuno Gomes Talk: Cave Diving World Records

Find your Dare: Verna van Schaik at TEDxSoweto 2013

Be sure to check out Nuno’s autobiography, BEYOND BLUE: Journey Into the Deep, which includes a lot of important cave diving history. 

Michael Menduno/M2 is InDepth’s editor-in-chief and an award-winning journalist and technologist who has written about diving and diving technology for more than 30 years. He coined the term “technical diving.” 

His magazine aquaCORPS: The Journal for Technical Diving (1990-1996), helped usher tech diving into mainstream sports diving and he produced the first tek.Conferences and Rebreather Forums 1.0 & 2.0. In addition to InDepth, Menduno serves as an editor/reporter for DAN Europe’s Alert Diver magazine, a contributing editor for X-Ray mag, and writes for He is on the board of the Historical Diving Society (USA), and a member of the Rebreather Training Council.

Nuno Gomes is a professional civil engineer, a CMAS technical diving instructor and a commercial diver. He was born in Lisbon, but his family relocated to South Africa during his youth. He now lives in New York, permanently, with his family. He has done all types of diving all over the world.

He used SCUBA (open circuit) to dive to a depth of 321.81 meters (1,056 feet), inclusive of rope stretch, in the Red Sea off the coast of Egypt near Dahab, in June 2005. The total dive time was 12 hours and 20 minutes. The descent took 14 minutes with two minutes spent at the bottom.

He also used SCUBA (open circuit) to dive to 282.6 meters (927 feet) in the Bushmansgat cave, in South Africa, in 1996. The cave is located at an altitude of 1,550 meters (5,086 feet) above sea level, which resulted in a decompression schedule for an equivalent sea level dive to a depth of 339 meters (1,112 feet) in order to prevent decompression sickness. The total dive time was 12 hours and 15 minutes with four minutes spent at the bottom of the cave.



Located high in the Sierra Mazateca mountains in Oaxaca, Mexico, Sistema Huautla has captured the imagination of elite cave explorers for more than 50 years. Join photographer SJ Alice Bennett and cave/tech instructor Jon Kieren on Beyond The Sump’s recent March/April 2022 expedition to Sump 9.




Text by Jon Kieren. Images by SJ Alice Bennett.

🎶🎶 Pre-dive Clicklist: 붐바야 (BOOMBAYAH) by BLACKPINK curated by Steve Lambert

Sistema Huautla, in Oaxaca, Mexico, one of the most iconic and expansive cave systems in the world with over 30 entrances, more than 100.7 kilometers/62.5 miles of known passage, and reaching a depth of over 1500 meters/5000 feet, has been an obsession for cavers around the world for over 50 years. Every year, several groups such as Beyond the Sump (BtS) and Proyecto Espeleológico Sistema Huautla (PESH) mount expeditions to the region to explore. Surrounded by karst topography with several other gigantic systems, such as Chevé and Kijahe Xontjo are close by, there is surprisingly only one main exit point for the water flow (based on several dye trace studies), the Huautla Resurgence. Huautla is still being actively explored from the plateau to find the allusive connection with its resurgence. Terminating in a 9th sump at 81 m/264 ft depth, it is logistically extremely difficult to push the end of the line from there. This leaves exploration from the resurgence as the most likely tactic to make the connection.

Santa Ana Cuauhtémoc.

Nestled deep in a canyon 1200 m/4000 feet below the sleepy little town of Santa Ana Cuauhtémoc in the Sierra Madre de Oaxaca mountains in Oaxaca, Mexico, is the Santo Domingo River. The Santo Domingo is fed by multiple water sources from various cave systems in the area including the Peña Colorada, Agua Frio Resurgence, HR Resurgence, and the Huautla Resurgence. The Huautla Resurgence was first explored in 1982, followed by expeditions in 1984 and 1995 led by Bill Stone. In 2001, Jason Mallinson and Rick Stanton pushed the cave to a maximum depth of 65m/215 ft and reached a sump pool where a dry cave passage heading off could be seen 10m/30 ft above, but with vertical muddy walls stopping the divers from being able to exit the water. Beyond the Sump, expeditions began exploring the resurgence in 2016 and 2017 where they found an exit from Sump 2 into a dry section, named “Passage of the Cheeky Monkey”, which was thoroughly explored and mapped, with several sumps found along the way. When time ran out for the 2017 expedition, several questions remained unanswered. Primarily, “where the hell does all the water come from?”, as the only source of water seemed to come from a small flowstone restriction affectionately named the “Squirty Hole”. A question that would need to wait five years to be answered.

In late March, 2022, Beyond the Sump set off on another expedition to Santa Ana to find the way on to “Sump 9”. The team consisted of Andreas Klocker (AUT/AUS), Zeb Lilly (USA), Steve Lambert (USA), SJ Alice Bennett (UK/GER), Ben Wright (UK), Rob Thomas (UK) and myself, Jon Kieren (USA), with logistical support happening remotely by Alejandra “Alex” Mendoza (MEX). Bios on the team can be found at: Beyond The Sump-Team. This is a log of our experiences and discoveries.

The team posing during a quick pit stop on the way from Tehuacán to Santa Ana.

28 March, 2022

The entire group met for the first time in Tehuacán. Andreas, Zeb, and Steve had driven down from the US, while SJ and I had driven over from Tulum, and Ben and Rob had flown in from the UK. Everyone’s travel up to this point was relatively uneventful, except for SJ. She had managed to badly sprain her ankle the night before, leaving us questioning how the first couple of weeks of the expedition would pan out for her. Both trucks were packed tight, but room was made for the Brits and SJ’s swollen ankle for the remaining four-hour drive up through the Sierra Madre mountains to Santa Ana. The drive is spectacular, beginning on the north western side of the mountains where it is an arid desert filled with giant cactus and ending at an elevation of about 5200 ft in a lush green mountain forest.

After a quick stop for tacos and to grab a “few” bottles of mezcal, we arrived at our field house after dark. We quickly scrambled to unload the trucks into the concrete box we would call home for the next four weeks. We hastily set up our beds, and a bottle of whisky and mezcal made a few quick passes around the room to con- gratulate our arrival before lights out.

Sunrise view from the field house.

29 March 2022

Church bells rang at 5:30 am which woke both us and the surrounding livestock as the sun began to rise through the canyon below us, a truly remarkable sight that I highly doubted I would ever grow tired of. First order of business was to dig out the coffee pot and tea kettle. Once adequately caffeinated, we started organizing all of the equipment for base camp and diving. We set up a makeshift kitchen with two small camping stoves and a fold-out table. After a batch of scrambled eggs were devoured, everyone started tearing into the dive equipment and getting personal kit and team resources organized. We assembled a boosting station in the field house and set the compressor up outside. Regulators, cylinders, and rebreathers were scattered everywhere, and SJ was busy with camera equipment. Morale was high as everyone made predictions for what the cave was going to do.

Sleeping quarters in the field house.
Andreas organising gear for the first dive day.
Steve packing the truck while brushing his teeth.

Steve, Zeb, and Andreas were supposed to have a meeting with the town council to finalize permission to use the road leading down the canyon and set up operations in the cave. We had no doubts we would gain permission, but it was important to play the local politics and stay friendly with the community. The meeting didn’t happen, but we were assured “mañana” (which often means “later” as opposed to the direct translation of “tomorrow”). Instead of holding the meeting, Steve, Zeb, and Andreas were handed a bottle of moonshine made from sugar cane, called aguardiente. In an effort to be diplomatic, they graciously accepted a drink, and then another. Soon they were hooked into a few hours of hilarity trying to socialize in broken Spanish while the rest of us waited patiently for word on what our plan would be for the next day. We would need to wait until 5:30 am when the church bells rang to assess everyone’s energy levels and see what we thought about the “beg for forgiveness” tactic for finalizing permission before deciding to head down into the canyon or not.

30 March 2022

We decided to go for it and started to set up in the canyon. The 1219 m/4000 ft descent down to the canyon took about an hour by 4×4 truck and was absolutely breathtaking, second only to the hike to the resurgence. The hike was a fairly easy- going 1.2 miles, but took about 40 minutes each way with heavy loads and several river crossings. Luckily, we were able to keep most of the heavy kit in the cave for the majority of the expedition with only CCR bottles, the “cave cascade” (a few lightweight high pressure carbon cylinders we had set up in the cave to refill cylinders), and other little bits and bobs of personal kit needing to be transported in and out each day.

Andreas, Steve, and I did the first dive to reline and survey the first sump and rig the waterfall. Upon surfacing at the waterfall, a wave of “holy shit, this is remote” hit me quite hard, and the smile would not come off my face. While we dove, the rest of the group (minus poor gimpy SJ, who was stuck at the field house knotting line) did two more gear hauls from the truck. Everyone was pretty beat, but nothing a couple Victoria beers and a few liters of gatorade wouldn’t fix.

In the evening, we were able to meet with the local officials for formal permission to use the road and access the cave. We donated some pesos to fund their annual celebration of the anniversary of Emiliano Zapata, which we also had to promise to attend.

Despite Steve’s insistence on K-pop for our daily soundtrack, morale was high.

The 4×4 squeezing out of the narrow driveway on the way to the canyon.
The road down the mountain was often shared with cows and horses. Or broken down cars.
Ben and Jon scrabble over boulders towards the cave.
The second river crossing.

31 March 2022

Day 2 of diving was productive. Zeb, Rob, and Ben were able to set up the gear line for the far side of the waterfall to hang the deep bailouts, run line to 140 feet, and set the deep bailouts. Andreas, Steve, and I did a few gear hauls through the canyon. The next day, Steve and I planned to reline and survey the second sump out another 1200 feet or so at a max depth of about 215 ft. I was excited for the “real” diving to begin.

Rob preparing to go under.

1 April 2022

Instead of the fiery red sunrise through the canyon, we were suddenly in the clouds and surrounded by cold mist, chugging coffee and tea but still struggling to wake up. The group appeared tired from the few days of intense hiking in the canyon, but moods lightened as the coffee hit, and we started to think about today’s dive. After today, we would likely begin pushing the leads left over from 2017 and searching for the way on to Sump 9. I was a bit apprehensive about making it over the waterfall with my Fathom CCR on, and felt a bit jealous of the side mount and chest mount units other team members were using. The waterfall was only about a meter high, but had high flow and razor sharp jagged rocks protecting it. I figured if it was a big hassle, I’d switch out my Flex2 side mount unit for future dives to make getting to sump 2 a bit easier.

On our drive down to the canyon, we were stopped by a group of enthusiastic locals. With big smiles on their faces, they insisted we get out of the truck and follow them up a small trail in the mountainside. As we followed, we could see smoke coming from a pit, and a strong scent of something sweet in the air. The group wanted to show us how they were processing sugar cane to produce piloncillo, an unrefined sugar commonly used in Mexican cooking. We were given a block of the piloncillo, which we later used to make syrup for pancakes and French toast when we started getting tired of scrambled eggs.

Steve and I had a great dive. We crossed the waterfall to sump 2. I made it over with my Fathom on, but it took a bit of effort. I was thinking that switching to the Flex for the next dive would make life easier, especially if we would be hauling more cylinders and scooters over the waterfall. Sump 2 was just a truly stunning, big passage with rolling hills all covered in silt. Our max depth was 56 m/183 ft on this dive, with about an hour of deco to do upstream of the waterfall. We laid another 365 m/1200 ft of line while swimming, setting up the next team to re-line all the way to camp 1 in the Passage of the Cheeky Monkey, and check what was thought to be the most promising lead discovered in 2017, referred to as the “11 meter lead”.

Andreas and Jon during a clean up dive hauling gear back over the waterfall.

2 April 2022

SJ came down into the canyon for the first time today. Her ankle was still in pretty rough shape, but life in the box on the mountainside had become dull. She had been as productive as she could be by knotting line and photographing the town. She also managed to make no less than four new boyfriends, led by a 6-year-old who kept bringing his siblings and friends into the field house and proudly exclaiming “gringa!” while pointing at SJ. He then would lead them around the field house showing off all of the strange equipment we had scattered about.

SJ trying to stay sane while knotting line and being stuck at the field house during the first week.

On our way into the canyon, we were hailed by another group of farmers just a little down the road from the piloncillo farm. As they enthusiastically led us to their farm, we could smell the pungent aroma of fermenting sugarcane before we could see the still. They first showed us how they crushed the sugarcane plants to extract the juice, which we sampled. Rich, sweet, and syrupy, it was hard to get down with the thought of the hard hike through the canyon ahead. Next, they showed us where the fermentation was taking place in large tubs next to the still. We were offered a sample straight from the still, which we had to decline, as there was much work and diving to be done yet. So we promised to stop back at the end of the day to have a drink.

Squeezing sugar cane into juice before the fermenting process.
The team watches with great interest.

The diving for the day proved to be less productive. SJ was able to take some photos of the canyon and divers prepping to enter the cave, but the dive was called early due to a rebreather failure. The line was still extended a few hundred feet, so all was not lost. But the line still did not reach the Passage of the Cheeky Monkey nor had any leads been investigated. Morale was a bit low.

At the end of the day, we stopped back at the aguardiente distillery and were poured a fresh bottle to be passed around. Before taking a drink, Steve asked how much alcohol was in it. The man proudly proclaimed “22 grado,” which Steve interpreted as 22% and took a chug. His eyes went big, he handed it to me, and I took a big swig for myself and quickly realized that “22 grado” does NOT equal 22% as I handed the bottle on to the next person. Realizing we needed to leave ASAP or it would be unlikely any of us could drive the truck home, Rob (who seemed quite pleased with the aguardiente) offered to buy the bottle to take home with us. With the transaction complete, we headed back up the mountain to get to the bottom of this “22 grado” business.

Steve organising his dry suit in front of the cave entrance.
Andreas’ pre-dive excitement.

3 April 2022

Another cold and cloudy day. I was tired, and my back felt broken when heading down the mountain. I needed a day of rest but knew we needed to push on. I switched to the Flex and headed in with Steve on DPVs to line the cave to camp 1 and check the 11 meter lead. I immediately realized I was overweighted with the Flex, steel side mounted bailout cylinders, and extra safeties and deco gas that were to be installed in sump 2.

Crossing the waterfall, I tore the right ankle of my drysuit, which I noticed as soon as I got back in the water on the other side. Knowing I had heated undergarments on and plenty of battery power for the couple hours of deco we might end up with, I decided I would be fine to continue the dive.

With each stage drop, I hoped my stability would improve, but it didn’t. I struggled on, Steve and I making it to the far side of sump 2 to search for the way on to Cheeky Monkey. We made our way up what we believed to be the correct path, doing our deco as we circled up towards an air bell. We did not find the 11 meter lead where we thought it would be, and realized we were in an area known as “Jason’s Eyes,” a dry section first discovered in 2001 by Jason Mallinson which had no way on. Steve asked if I wanted to surface to look around and chat about where to look next, and I reluctantly raised my thumb and pointed back toward the exit. I was super uncomfortable being overweighted as well as needing to dive back to 65 m/215 ft and have an hour or so of deco before the waterfall with a flooded drysuit. Plus, I knew that if we dragged this dive on much longer, I was going to start making mistakes. So we re-descended from our 3 m/10 ft stop and headed back toward Sump 1, when I was abruptly stopped at 9 m/30 ft as I could no longer inflate my wing or drysuit.

Grabbing the cave wall, I realized that the two liter cylinder I had dedicated for wing and suit inflation was dead, clearly a result of struggling with being overweighted and unstable. I got Steve’s attention and communicated the problem, and we started to inventory resources with an LPI connection. We had an O2 bottle, which would not be great for suit inflation considering I was already shivering in the 18º C/65º F water and would desperately need to use my heat during deco. The 50% bottle we were to drop at the deco station heading to camp 1 only had a QC6 connection, which would be no help to me. And that left only my side mounted bailout, which was 15/55 trimix. Certainly not ideal for suit inflation, but better than starting myself on fire. I plugged in and filled my suit with the icy trimix as we started to exit. I had to constantly switch the hose from my suit to wing as we scootered out but managed to make it back to the waterfall with only an hour of deco, which was manageable with my heated vest on full blast.

Jon getting dressed before a not-so-great dive.
Steve getting in the zone.

We were unsuccessful in completing our tasks for the day, and I was in a world of self-pity from my poor decision to change configurations without a shakedown dive. We went back to the field house to conduct some experiments regarding the actual alcohol content of the Aguar. Tomorrow we would rest and re-group. Morale was low.

8 April 2022

The past few days had been challenging. Several attempts at exploration in Sump 2 had proven unsuccessful. We had scoured the deep section, and the fabled 11 meter lead, and others like it, which all pinched off quickly. While there was significant flow coming out of these tight passages, they were simply Swiss cheese that was not passible by humans. Maybe after a few hundred thousand years or so, they would be big enough so we could jam Steve in there to take a look, but for now, we were going to have to focus our search in the Passage of the Cheeky Monkey and the sumps within it to find the way on.

Logistically, this would mean exploring from camp 1 to avoid having to pass a waterfall and do a 65 m/215 ft dive prior to surfacing and hiking gear a couple thousand feet through dry cave to the Sump each day. We would be using the next day as an opportunity to rest and get the first camp team, Rob and Andreas, ready to set off for a couple of days in the Cheeky Monkey.

SJ’s ankle was feeling well enough for her to dive, so we’d done a couple of shakedown dives to test the ankle and get a feel for the cave before starting to shoot the next day.

Steve and Zeb making an aguardiente offering to the cave for good fortune.
Zeb and Steve mixing cave dinner and packing dry tubes for the first camping attempt.

9 April 2022

SJ and I entered the water for a photo dive shortly after Andreas and Rob pushed off for camp 1. About 30 minutes into shooting, we noticed lights and the sound of scooters buzzing toward us. It was Andreas and Rob, obviously having had some sort of problem and aborting early. We decided to exit with them to see if we could assist somehow. Turned out they had a dry tube failure when they made it to the end of Sump 1, drowning most of the camping equipment.

With only 9 days of diving left, and time starting to run out, we couldn’t afford any more mishaps if we were going to figure this cave out. A serious team discussion was had to decide on the schedule for the next few days to prioritize exploration, as well as to ensure that we would have opportunities for documentation. We planned to prep and re-group again the next day, then Steve, Zeb, and I would head into camp 1 for a very long day of poking around in the Cheeky Monkey to determine what the objectives should be for the first camping team.

Steve watching as Andreas and Rob descend on the way to camp 1.
Jon swimming out of the cave though the first arch.
Jon swimming though the double arches in Sump 1.

In the evening, we had a chance to meet up with Bill Stone and his team who were exploring a nearby dry cave. It was pretty surreal to be in Oaxaca with Bill, hearing him tell stories of exploration in the area, as well as to discuss what we had found and what we thought the cave might do. Bill was convinced the Swiss cheese we had found could not be the only water source, as it was rumored that during the rainy season the resurgence produced a geyser several meters tall. We discussed what our plans were moving forward, and Bill seemed to agree that the sumps in the Cheeky Monkey must be hiding something.

10 April 2022

A day of rest and prep for a long day tomorrow. There was a celebration in town for Emiliano Zapata with parades, fireworks, and lots of mescal and aguardiente. It began last night and never really ended. We were supposed to attend the festivities that evening, but hopefully only for a short while as we were planning to leave the field house at daybreak to be in the water early morning.

The music and festivities in town added a joyful feel to the somewhat mixed emotions in the field house. Excitement, stress, and anxiety. Morale was pretty high considering the pressure we were under.

A festive parade walking down the mountain through town.
Tacos were hugely enjoyed by the team.

11 April 2022

A long but successful day. Steve, Zeb, and I pushed off early in the morning and spent the majority of the day in Cheeky Monkey. From the beach where we surfaced, it was about a 30-minute hike through fairly rough terrain, but no serious climbing required. Hauling dive gear did create some challenges, though. We checked Surprise Sump first, which had not been dived before, and it turned out to be the biggest discovery we’d had the whole month. Immediately upon descending, Steve noticed darkness beyond the duck under in front of him. As he shouted for joy through his loop and descended with a line peeling off the reel, hearts started pounding as we realized what might have been right under the team’s noses during the 2017 expedition.

One of the very many o-ring failures during the expedition.

After a hundred feet or so, it surfaced, followed by a short hike and another sump which had an upstream and a downstream, and then another waterfall on the upstream side. Not the borehole we were hoping for, but there was more cave here than we knew about the day before, so that was a huge plus, and it seemed to be heading in the right direction–toward Sump 9. Logistics would definitely get more interesting, but we had a good idea of what resources would be needed for the first camping trip. We exited the water a little after 6 pm with rejuvenated spirits and confidence that we were on the brink of breaking this thing open.

13 April 2022

SJ, Andreas, and I were supposed to do a photo dive today. On our way down the mountain, Zeb’s truck’s suspension started making some terrible noises. When we inspected it, we noticed the leaf spring hanger bracket had torn in half, leaving the leaf spring pressing up into the bed. With no option, we slowly drove the truck back up to the field house to start the process of finding parts and tools. After a quick team meeting, we made new plans based on best and worst case scenarios. Best case would be that the truck was fixed today or early tomorrow morning, and we could get a camping team in to push from Surprise Sump for a few days while SJ and I got as many photos as possible. Worst case, we wouldn’t have time left for camping and would have to do the best we could with a couple of day trips.

A very broken bracket.

SJ and I drove down to Tehuacan to pick up a new bracket while the team tried to get the old one off. At the suspension shop, I was struggling to communicate with the woman at the parts counter. She seemed to know what we needed, I was just trying to verify the part number to be sure we weren’t about to make a 7-hour round trip and return with the wrong part. A kind man waiting in line asked us in decent English what we needed, and I explained. He said, with a sly grin and a wink pointing at the woman behind the counter “she knows”. The woman looked at me and smiled. I shrugged and nodded as she grabbed the bracket and darted off while saying something to our new friend. He told us she took it in back so the shop could press the bushing into the bracket for us. While we waited, we chatted with the man about what we were doing there. He seemed intrigued, was enjoying the stories of our adventure, and I was showing him some photos of caves in Tulum on my phone, when the woman returned with the bracket. As I was paying her, two young men were trying to give SJ a couple sandwiches and pepsis. When she tried to refuse, the woman behind the counter got very excited, gesturing for us to take them. Apparently, when we said we had come 3.5 hours down the mountain to get the part, they were empathetic to our situation. And based on my ragged clothes, matted hair, tired face, and sand-fly covered body (SJ looked great as always), they must have assumed it was quite the journey and refused to let us go away hungry and thirsty.

When we got back to Santa Ana, the team let us know they were unable to pull the old bracket, and that we’d have to take the truck to the nearest town with a mechanic first thing in the morning to try to repair it.

Team discussions in the field house.

14 April 2022

It took until about 2 pm to get the truck fixed, but determined to get some work done, Steve, Zeb, and Andreas decided to push off for camp 1. They were in the water by 6pm, planning to reemerge on the 18th at 4pm.

Zeb stuffing a dry tube with Jon posing questionably in the background.

While driving the truck back up the mountain, I noticed the brakes seemed a bit soft and the steering a bit stiff. However, this was my first time driving Zeb’s truck, and without much other choice, I kept making our way back up to the field house. When we arrived at the house, it was noticed that power steering fluid was leaking below the truck. By then it was after 8 pm, and there really wasn’t much we could do about it at the moment anyway, so we all promptly crashed out so we could get up early and try to sort out the problem in time for SJ and I to finally get in a proper photo dive.

15 April 2022

We topped off the hydraulic fluid but were unable to determine the source of the leak. Ben and I drove the truck around on the more benign roads at the top of the mountain with no noticeable leaks or ill effects on the steering or brakes. So we made the decision to head down the canyon and take some pictures. SJ on the camera, me on lights, and Ben as a model. All went off without a hitch, and the truck made it back up the mountain with still no signs of a leak. I was happy about that, but quite wary. As my dad says, “Problems don’t usually just fix themselves…”

Ben swimming above river pebbles in the cave.
Ben ascending one of the many ups and downs in Sump 1.

16 April 2022

A day for surface photos. SJ had plans to photograph the canyon as well as take some simple shots in the cave entrance. It was a light and easy day that should have wrapped up quite early. However, as we started to pack up and leave the cave for the day, two by two, our entire host family, all 13 of them, started coming around the corner walking toward the cave. It was surreal, we hadn’t seen a single other human in the canyon for weeks, and there out of the blue, was the whole family. Dragging half sleeping children, the happy and excited adults hastily climbed the rocks up to the cave entrance. They were amused to hear that our friends were several kilometers underground and wouldn’t return for a few days yet. After a bit of climbing around, we all started to make our way back down the canyon toward the truck. After the first river crossing, SJ noticed one of the young mothers struggling to carry Liam, the two-year-old. She gave me a nudge, and I turned and offered to carry the little guy. At the next river crossing, we noticed they had a whole camp set up at the edge of the river. As we approached, the young mother offered us a drink, took Liam back from me, and before we knew what was happening, they had reignited the campfire stove and were preparing a late lunch for us. We ate some of the most amazing refried beans on the planet while the kids played in the river until the abuela (grandmother) started packing up a few things. I looked at her and asked “vamos?” (We go?), to which she loudly exclaimed “VAMANOS!” (Let’s go!) With a smile on her face, as everyone scrambled and had camp packed up and were hiking again within moments.

Ben showing the small cavern and explaining that the three missing team members are camping in the cave right now.
Late lunch on the way back at the family’s camp.

After encountering the family, our day suddenly became much longer than we had anticipated. We got home after dark, exhausted from another hot day hiking in the canyon, yet rejuvenated from the experience we had just had. It had been hard to keep morale up with the never ending issues we encountered, as well as less than stellar productivity, but to be able to share a bit of what we were doing there with our caring and supportive host family was truly an experience. They thought what we were doing was truly remarkable, which it really was; it was just hard to remember that when facing failures and adversity. So, a little reminder by way of the smiles on the faces of our new friends gave us quite a boost. We ate dinner quickly and settled in as early as we could. One more shot at cave photos the next day. Before Steve, Zeb and Andreas come out and mess up the vis hauling all of their camping gear out.

Jon swimming into the cave through the first arch.

17 April 2022

SJ and I were able to get in a nice long photo dive. As we were packing up to head out, we saw lights flicker below the surface. Steve, Zeb and Andreas were back a day early, not necessarily a good thing…

Jon’s HUD glowing while swimming through Sump 1.

As they emerged, one by one, there were no high fives or cheers of joy. Just a content look on Zeb’s face as he calmly stated in his mild southern drawl, “she doesn’t go”.

Arriving at camp 1 after 8 pm on the 14th, they had set up camp and prepared for the following day’s explorations. Over the next two days, they scoured the Passage of the Cheeky Monkey and the sumps within.

They dived Surprise Sump, the newly discovered Gold Star Sump, as well as checked the stream way beyond the new waterfall, and searched every corner of the dry cave. The downstream section of Gold Star Sump pinched off into swiss cheese where there was a significant amount of flow. The stream way beyond the waterfall also pinched off into another flowstone restriction, similar to the Squirty Hole. No new sections of dry cave were discovered. Based on observation of the amount and direction of flow exiting downstream Gold Star Sump and the small restrictions in Sump 2, the team estimated it is approximately equal to the flow coming over the waterfall in Sump 1 as well as exiting the resurgence. Concluding that all water sources have been discovered, none of which will allow a human to pass, and no passable dry cave is accessible.

Disappointed, but content that every corner of the Huautla Resurgence had been checked, they decided to close the book on the project and head out a day early.

Visibility got worse with the water levels dropping towards the end of April.

The next few days were dedicated to more photos and cleanup. With 12 safety and deep bailout cylinders remaining in Sump 2, scooters staged at the waterfall, several safeties in Sump 1, six shallow bailout cylinders, rebreathers, and personal gear for seven divers left in the cave entrance, there was a lot of work to do. However, with teamwork, we managed to get everything out of the canyon in just three days. Our backs a bit sore, and our dreams of big going borehole passage beyond Sump 2 unrealized, moods were a mix of relief to be finished and a reluctance to leave, knowing we would likely never have a reason to return to this truly remarkable site.

Completing a project is a bittersweet feeling, of course. While sad there’s no more cave, there’s also a feeling of content completion. We did everything possible to find the way to connect the resurgence to Sump 9 of Sistema Huautla, and we are probably the last team to ever see the inside of the resurgence for the foreseeable future (or ever), which is pretty damn cool. We also had the opportunity to spend time with new friends in a truly remarkable place with extraordinarily gracious hosts. So, in all, I would certainly call this year’s Beyond The Sump expedition a success.

Jon swimming through a tunnel in Sump 1.

Additional Resources:

Wikipedia: Sistema Huautla
Explorers Club:Sistema Huautla, Mexico – the 50-year original exploration and study of the deepest cave in the world
NatGeo:One of the Deepest Caves in the World is Even Bigger Than We Thought

Exploration groups involved with Sistema Huautla:

Beyond The Sump |
Proyecto Espeleológico Sistema Huautla (PESH) 
United States Deep Caving Team

SJ Alice Bennett has been photographically documenting the world around her since she was a kid. After completing a diploma in Graphic & Communication and a B.A. in Visual & Motion Design and moving to Quintana Roo, Mexico in 2017 she’s turned her focus on the underground rivers of the area. Her documentary style of shooting is well known for capturing the emotions of the moment and creating a sense of being there with her. She has a passion for documenting exploration and has worked as a freelance photographer and graphic designer around the globe and just joined the InDepth team. Watch this space.

Jon Kieren is a cave, technical, and CCR instructor/instructor trainer who has dedicated his career over the past 13 years to improving dive training. As an active TDI/IANTD/NSS-CDS and GUE Instructor, and former training director and training advisory panel member for TDI, he has vast experience working with divers and instructors at all levels, but his main professional focus resides in the caves. In his own personal diving, Jon’s true passions are deep extended range cave dives (the more deco the better), as well as working with photographers to bring back images of his favourite places to share with the world. 

Continue Reading

Thank You to Our Sponsors


Education, Conservation, and Exploration articles for the diving obsessed. Subscribe to our monthly blog and get our latest stories and content delivered to your inbox every Thursday.

Latest Features