I have always felt particularly lucky.
For example, my originally scheduled trip to Mexico was missed due to a scheduling conflict with JJJ and the Navy, and I couldn’t find any other Cave 2 level buddy after asking around. In my frustration, inspiration struck, and I emailed my Cave 2 instructor Danny, hoping against hope to see if I could arrange a private guided dive. Danny replied, saying, “Sure, how many days do you want?”
Looking back now, this twist of fate was undoubtedly one of the wisest decisions of my diving life.
During this trip, I stayed at a small hotel in Tulum. One morning, a German girl in the next room caught me for a chat: “You are here for cave diving, how are the caves here?”
I thought for a moment and replied with one word:world-class.
(Image from: Smart et al. 2006, Cave Development on the Caribbean coast of the Yucatan Peninsula, Quintana Roo, Mexico)
This image shows the relative locations of Mexico, the Yucatan Peninsula, Quintana Roo, and Tulum. Most of the best diving caves in Mexico are located in the easternmost province of Quintana Roo, especially around Tulum.
(Image from: Smart et al. 2006, Cave Development on the Caribbean coast of the Yucatan Peninsula, Quintana Roo, Mexico)
This image illustrates the cave systems (Sistema) mapped in Quintana Roo province as of 2006, typically located within 12 kilometers of the coastline. Since then, many new caves have been discovered, and existing systems have been connected, such as the Ox Bel Ha and Yax Chen East systems connected by MCEP and CINDAQ in 2007, and the BilPhilips and Steve Bogaerts with Naranjal system connected in 2011. As of July 2016, the entire Ox Bel Ha system, with a length of 270 kilometers, ranks as the longest explored underwater cave in the world, followed closely by the Sac Actun system, which now has over 257 kilometers of mapped passages.
Some locations in these underwater cave systems have roof collapses, exposing them to the surface, and are known as cenotes. The Ox Bel Ha system has 143 of them. Those cenotes that are large, clear, and easily accessible often become tourist hotspots, like Gran Cenote in Sac Actun, and Casa Cenote at the mouth of the Nohoch Na Chich system, which are great spots for non-divers during hot weather. When I took the Cave 1 course during the summer, I carried heavy double tanks, dressed in thick dry suits, watching bikini-clad beauties playing in the cenote, feeling like I was putting myself through unnecessary hardship.
Of course, without enduring that hardship, how could one experience such a wonderful world today?
There are also a few cenotes that do not belong to any known cave systems, called pit cenotes (not referring to the famous The Pit in the Dos Ojos system), where the water does not flow. The organic matter accumulating at the bottom is anaerobically decomposed by bacteria, producing hydrogen sulfide that continuously accumulates, forming a thick, fog-like layer of hydrogen sulfide around the halocline, creating a spectacular view. The most famous spot is Angelita, where countless heroes have posed.
By the way, hydrogen sulfide really stinks; a friend named Angelita came up from a dive and immediately threw up. Don’t ask me; I didn’t go there. I’ve already smelled enough of that in the mine, and at times like this, I really envy those buddies with nasal allergies…
There are many limestone layers around the world, and the scattered caves are not rare; you can see them in most karst areas. However, there is nowhere else in the world that has the unique cave diving conditions of Quintana Roo.
The underwater caves here leave a lasting impression of extreme beauty on most people. Unlike the underwater caves in Guangxi and Guizhou, these caves mostly formed on land and were later submerged due to changes in sea level, resulting in stunning stalactite formations that cannot develop underwater, preserved in pristine condition.
The first time I went to Mexico, the most impressive was Nohoch Na Chich. This is a pure white stalactite cave, and as I swam upward, I was dazzled by the sights. The second time I visited, I could enter the famous Room of Tears in the upstream cave of Carwash, named for its breathtaking beauty, and naturally, the scenery goes without saying; you can find many photos online. However, by this time, I had started to feel a bit of aesthetic fatigue and found the ancient fire pit sites in the downstream cave of Carwash more interesting.
(Ancient fire pit site in the downstream cave of carwash. Used with permission from photographer Daniel Riordan, please do not repost.)
About a hundred meters into the cave, after passing through a narrow passage that can only accommodate one person carrying double tanks, there is a round pit carved into the central rock, containing charcoal remnants that are distinctly different from the surrounding rocks. Archaeologists believe this is a site of ancient human rituals. I once asked Danny: “Won’t lighting a fire this deep in the cave consume all the oxygen and suffocate us?” Danny replied: “That indicates that this cave is interconnected, allowing air (and later water) to circulate freely.”
Also, because most of the caves here formed above the water surface and later underwent erosion from the halocline (halocline) where saltwater and freshwater mix, most cave systems do not exceed a depth of 30 meters (except for a few like The Pit). This means that extensive exploration can be conducted here without the need for large amounts of gas and decompression — Danny and I each carried four 11-liter tanks (double tanks + two stage tanks), totaling around 9000 liters of gas, allowing for dive times of up to three hours, with pure oxygen decompression time not exceeding 20 minutes.
Of course, I won’t tell you about the time I got my face bitten by a hungry catfish while decompressing at a cave entrance, leaving three holes in my face…
Speaking of the halocline, the most memorable experience was in the Ponderosa system at River Run; there is a long passage crossing the halocline, with freshwater flowing out to sea above and saltwater flowing in from the sea below, moving in opposite directions. So when you sink into the lower layer of seawater and look up, you see a clear river flowing overhead, making it feel like you are in a magical realm.
Even if you only stay in the cavern zone and do not enter the actual cave, you can still see the halocline. Just remember, the closer you are to the sea, the shallower the halocline, making it easier to see. However, be careful not to go to the previously mentioned Nohoch Nah Chich; the upstream depth there is only 5-9 meters, far from the halocline depth; you have to crawl through Hell’s Gate to reach the lower cave to barely access the halocline. Diving in the middle of the halocline is not a good idea; if a teammate kicks up, the freshwater and seawater mix, turning the visibility murky for those behind.
Similar to Nohoch Nah Chich, many systems have upper and lower layers or even multiple layers of passages, like the previously mentioned Carwash, where countless people have taken photos of the water plants; the water shines with blue light from Mayan Blue, connected to the pitch-black Jailhouse, and my favorite Tortuga.
Unlike the clear entrances commonly seen, the entrances to Jailhouse and Tortuga are unremarkable small puddles, with visibility within six meters comparable to Qiandao Lake. Danny was worried I would get lost, so he insisted I follow the rope down to six meters. Of course, as someone who has dived in Qiandao Lake with a DPV and even lost it several times, this was nothing…
(Entrance to the Jailhouse cave. Copyright belongs to me, please do not repost.)
(Passage in the Jailhouse cave. Used with permission from photographer Daniel Riordan, please do not repost.)
The entrance to Jailhouse at least has a wooden ladder and rope, allowing me to climb out; however, the entrance to Tortuga has nothing, and I looked at the huge rock with some worry. Sitting by the entrance of Tortuga, Danny drew maps while telling me a sad story.
(Entrance to the Tortuga cave. Copyright belongs to me, please do not repost.)
The previous owner of this land was a very old grandfather. (Some buddy interrupted my story: “The current owner is already very old!” I shot him a glance: “It’s the current owner’s father!”)
The old grandfather couldn’t swim but loved the water. So he placed a ladder at the entrance and would go down to soak in the water every day. Later, as he got older, his family became very worried and told him not to go, but he wouldn’t listen. One day, Danny brought people to the entrance, only to find the door tightly closed, so he had to go back to his house in Tulum to get the key. The old grandfather’s family told him: “He didn’t come back last night around seven or eight o’clock; his family went to the entrance to look for him and found he had drowned in the water, probably from falling off the ladder and hitting his head. His body has been recovered, but his dentures are missing; the family asked Danny to help retrieve the dentures.”
After that, there was no longer a ladder at this entrance.
I also silently closed my mouth to complain.
Hiring Danny as a guide is not just because he tells stories; as a Mexican who is also a rare technical diving instructor, he speaks the local language and is well-versed in local culture. He is the initiator of MCEP (Mexico Cave Exploration Project) and the GUE cave diving training director, having explored underwater caves in Quintana Roo for over 20 years. He knows every entrance, every passage, every jump line, and how each segment of the journey has different scenery, such as where Jailhouse can be navigated through extremely narrow rock layers, or how the upper passage of Tortuga is spacious with rich stalactites, while the lower passage is narrower with many clay deposits and puzzle-like white rock fragments.
（Upper passage in the Tortuga cave. Used with permission from photographer Daniel Riordan, please do not repost.)
（Tortuga cave’s lower passage. Used with permission from photographer Daniel Riordan, please do not repost.)
He will teach me to shine my light upwards in areas with air chambers, then cover the light and watch how the light above flickers and fades, as if someone above is responding to your signals; he will let me turn off the light in certain places and use his light to illuminate the stalagmites, which are as translucent as jade; he will teach me not to shine lights on blind worms, blind shrimp, and predatory fish that have intruded from outside the cave, to avoid these small creatures, which have lived in the cave for thousands of years, from being extinguished in an unfair predatory competition…
He will also take me to passages that no one has entered since he first explored them.
Diving with the Explorer. For me, this is the most wonderful part of the trip.
Danny said: “I haven’t gone this far into a cave with four tanks in a long time because the people I usually bring have a gas consumption at least 30% higher than mine.” (Given that my gas consumption is comparable to that of a big man, I don’t have much to boast about…)
Danny said: “There are some passages that I explored and mapped with an elderly British lady over a decade ago, and some could only be accessed with sidemount gear. She should be…”87 years old now. Because the last time we came here, she was already 70 years old.”
Flipping over the arrow marker with the old lady’s name Ise, I suddenly felt a longing for retirement life, having always thought I needed to find a way to pass away before turning 60.
Because Mexico tells me: It’s never too late to explore.