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Exploring Earth’s insides: cave diving in Mexico

With more than 15 years of experience in diving and an exceptional passion for cave diving, Robert Schmittner is the epitome of perseverance. After conquering his initial disappointment when trying to get certified as a diver in Germany, Robbie’s determination brought him to Tulum, Mexico, where, after four years of hard work, he succeeded, together with his buddy Steve Bogaerts, to establish Sac Actun as the largest water-filled cave system in the world. Following, Robbie shared with his experiences in the caves of the Yucatán Peninsula and the story behind his search for a connection between Aktun Hu system and the Sac Actun system, which materialized in the beginning of this year (2011), making the cave the 4th longest in the world.


When did you start diving and why? Do you have any story attached to that moment?

I was always fascinated by Jacques Cousteau and Hans Hass movies. I did my first attempt to get certified as a diver in Germany, when I just turned 18. Unfortunately, I did sign up with an instructor which seemed to be an ex-military drill sergeant. He made me do the “controlled emergency swimming ascent” [CESA] from 18 meters, five or six times, the water was 4 degrees [C] cold (I’m in a wetsuit), the lake was half frozen. As blood was running out of my nose, after the last attempt I aborted the course. It took me almost two years before I took the initiative to try again. Then, I found a good instructor and did my Open Water Diver course in the fall of 1994.

Tell us a bit about your diving career. How did you decide to come/remain in Mexico?

As mentioned, I did my Open Water Diver in 1994 in Germany. Went then to the Maldives for my first diving holiday and really got hooked there! Right back from the Maldives I kept going, doing Advanced, Rescue, Divemaster and started working in my free time at the same dive shop where I had done my Open Water, close to my home town, Rothenbuch, a little village with 2 000 souls, close to Frankfurt.   

It happed to be that the owner of this shop and his wife, which was Mexican, decided to leave for Mexico and to open a dive center in Tulum. As I was frequently in their shop, had been an assistant and had become friends with them, I, of course, had to visit them and to see where they moved. Now, being in Tulum, I tried something new: cave diving (1996); at the time this was the coolest thing I had ever done! I was hooked again! And this time it was an even bigger “hook”! By the time I was flying home I already made plans to come back to Tulum and stay a bit longer, to get more of these unbelievable caves. My plans ripened to the point that I would like to become an Open Water Instructor, to go back to Mexico and be able to teach and make enough money to support my stay there. So, I landed in December 1998 at Cancun Airport with the idea to stay for a half year. 

The half year quickly became a year and a year became 13 years! Jesus, time is flying!

How is life for a German in Mexico?

Life is very good for me over here. I do not see myself as a German or a Mexican or any other nationality, I’m just me! Now, I’m a person which enjoys nature, warm climate and personal freedom a lot! Mexico has in this respect much more to offer for me than Germany. Plus, here I found my passion to discover places which have never been seen by human eyes before.  

Where comes from your passion for underwater speleology/caving; what is so special in caves, what attracts you? How did you start your explorations?

Well, I started as a “sports cave diver”, guiding cavern divers through the daylight zones of the cave entrances and teaching people Open Water and Advanced classes to make money to be able to live over here. But usually, right after work, I put my cave gear into the shop’s pickup truck, searched for a dive buddy and off we went, cave diving! These places where and are incredible! Trying to explain how they are will never work out! You can paint it in the brightest colors, but you could never make someone totally understand how it is hovering through this inner space! Some places totally look like you would imagine the Moon! Others like Mars, Pluto or Venus! And more then a dozen of these “star gates” are only a few minutes away from Tulum.

I couldn’t get enough of these caves. After a while I had to start solo cave diving, because I wasn’t able to find people which shared my enthusiasm, going cave diving every evening/night! So, I got to know the caves around Tulum and came more and more to places off the tourist tracks, where I could find places where the guideline ended, but the cave passage kept going. Or places where the guideline passed by a tunnel, which went away to another direction, but it had no line in it!

After a couple of cowardly attempts running a new guideline here and there, a Mayan man showed a total “virgin” cenote to Gunnar Wagner, the owner of the dive shop I was working for, and me. Entering this cenote an amazing new world opened its gates to us! The passages in there where huge, incredible decorated and went for kilometers and kilometers! We built a jungle camp and stayed out in the rainforest for more than a month. We found remains of a mastodon and giant sloth in there, which was published in National Geographic and some dive magazines. To say it very simple: WE HAD A BALL!

We’ve been working several years on this cave system and during this time I discovered my passion for exploring.         

At the beginning of this year you established another connection between the Aktun Hu system to the Sac Actun system of the Nohoch Nah Chich region, which became the 4th longest cave in the world. Tell us how this happened.

The connection! I first started diving from the outland cenote, the same place where divers enter when they like to dive to the Black Hole [Hoyo Negro] (correct name, Black Abyss is wrong), but instead of going against the water stream towards the Black Hole, I went downstream away from it. I kept going to the end of the already installed line, which was mostly placed by Mike Madden in 1996. The team which is currently exploring Actun Hu (Alejandro Alvarez, Beto Nava and Franco Attolini) is exploring the DIR [Doing It Right] way, in backmount gear configuration and at least in a team of two or three divers. Practicing this kind of exploring, they were not able to press on with the exploration on the end of the downstream line, because the line ended at a sidemount restriction. After checking out the area I went to see Alejandro Alvarez to ask permission to check if I can continue at the sidemount restriction. He didn’t see any problems there, so I went, pushed through the sidemount restriction and kept going.

In three dives I installed a bit more than a kilometer of line going south and after a while turning east where I wanted to go searching Sac Actun. At one moment I ran into another line in front of me, as I pressed trough a sidemount restriction, which was so small that I had to take one tank off to be able to get trough. I was really excited because I thought I had connected to Sac Actun already! But, as I surveyed the line where I connected to, to be able to find the connection place at the Sac map, I found out that I connected to another little system which I didn’t even know it existed. I surveyed all lines and found two cenotes connected together by Mike Madden in 1996. I was still around 200 meters away from Sac Actun.

One of the cenotes (two doors) was fairly big and I found two more water pools in the same depression, which no one had entered yet. So, I did! The pool on the north-eastern side (closest to Sac) was blowing water like crazy, strongest flow I have seen in our area. Following this flow I was able to get over to Sac Actun in only one dive. Now, I had two water pools inside the same depression, but they belonged to two different cave systems. At my second dive at the north-eastern pool I tried to get around the depression, back down south where I wanted to find the lines of Actun Hu. I was able to get around half way there. Then, I came to a restriction which I could not even pass, having both my tanks clipped off and in front of me. I was able to squeeze half way in there but that was it! I was convinced that I could pass through when I took my sidemount jacket off as well. But as I had still the possibility to find the same place from the other side I decided not to do it. A good thing was squeezing into the restriction, because I was able to see that on the other side of the restriction a nice side room has place and that there is at least enough room to turn around in case I will push through later. I could see as well a big bunch of tree roots coming from the ceiling of the cave. Another definite sign that there is cave going on the other side was the very strong flow of water pumping into my face. That water had to come from somewhere!

Now, after a different dive, where we were filming inside the two door cenote, I showed my friend Marty the other two pools and told him that one of them leads straight over to Sac Actun and that I have found some cave as well in the other pool, but that cave “walls out” after a while and didn’t connect to any other lines. So, basically, I had one depression with three pools, which are all part of different systems. As we are walking around the depression, I see a hole on the eastern side of the depression which I had never seen before. I looked into it and saw a big dry room behind it! As I went down into it using a flashlight, I found a beautiful big pool of water on the bottom of the dry cave entrance. This water was moving just as strong as it did inside the passage which led to Sac Actun or at the place where I couldn’t get through. You could see swirls on the water surface, which is very unusual for our region.

I don’t have to tell you that I directly entered this pool with the rest of the air I still had in my tanks from the filming dive. I first went into the flow and started exploring south. Right at the beginning of my dive a big loose rock blocked my way, but after a bit of work I was able to get it out of my way by rolling it down the depression. I kept going and only ten minutes later I found the line of Aktun Hu. To keep the visibility clean, when I tried to find the Sac line, I decided to climb out of the pool, which was the “Actun Hu pool”, I carried my gear across the depression with the help of my friend Marty and my brother Richie, and entered at the same pool (#4) again, where I had just started a dive 15 minutes earlier. I started exploring now with the flow going north. As I had gone for a little bit I found a chimney right underneath me, which definitely sucked water down into it and seemed to lead into a deeper layer of the cave. Unfortunately, this chimney was blocked by big rocks and broken stalactites. So, I pressed on searching another way down there where the water went. I couldn’t find another one! As I was low on gas by now, I decided to stop for the day and come back the next day. So I did and, as I didn’t find any other way, I went to the chimney and started to pull out all the loose material. After about a half hour I was able to fit (one tank in front) through the rabbit hole. On the bottom of it (6 feet/≈2 meters deeper) the passage turned sideways again and I was able to keep going. As all this work, moving things, had created a lot of suspended silt, I had a hard time finding my way through a pretty small cave. I was able to install another 50 meters and ended again on a very small restriction right in front of me. The water flow went with the described strength right into it. As this dive was mentally quite exertive I turned around and left the cave, collecting the survey data of the line I had installed.

In the evening I entered my data in the computer and could see that both lines, the one coming south from the Sac pool and the one I just installed going north, are pointing right at each other. Very strong flow going into a restriction on one side and very strong flow coming out of a small restriction on the other side! I was on the right way! For sure! The distance in-between them, due to the map was ≈20 meters/60 feet.

The very next day I went again to the place where I turned around the day before. When I got to the end of my line, I connected my new line to it and then I took off both my tanks right away, because this was the only way to get ahead. Squeezing through, a lot of silt came up again and was blown directly in front of me. Now I was exploring, pushing two tanks and a reel in front of me, feeling my way, because I couldn’t see, through a tunnel just big enough to fit through. I stopped several times, not moving at all, to allow the flow to clear the visibility a little bit again. So, I could see a little bit, but right by the next move the vis went 0 again. The first time it came to my head – “Screw the connection and turn around”, I still pressed on! “Damn, I must be so close!” When the second time it came to my mind, I actually decided to abort my dive and get the f*** out of there! Now, my problem was I couldn’t turn around! So I pushed forward feeling with my hand, trying to find a big enough place to turn. As I had found this place, l squeezed over to the side as much as I could to be able to turn side ways. But before I would do this I was going to wait a few minutes again to have a little bit of vis for my maneuver. As the visibility cleared I saw something which changed my plans to abort the dive immediately! Roots! The roots! The ones which I was able to see from the other side when I looked through the restriction! I had to go a little forward and actually make my way through the root-ball to pop out on the other side into the little room, which seemed like a giant hole at that moment! As I was in the room the vis was 0 again and I decided to hang positively buoyant under the ceiling of the cave, not moving, to get some visibility back. Two-three minutes later I went to the bottom of the room where I found the restriction, which had my line and arrow inside of it! I connected my line to it and cut it off! I was very happy about the fact that I had good visibility the whole way back, as I was surveying into the flow. The length of the installed was like the map said before: 20 meters! To install it took me 37 minutes and another 30 to survey it!

Tell us a bit about the cave diving environment.

The caves of the Yucatán are rather shallow, but very, very extensive and complex; some exceptions in depths there are. “The Pit” is the deepest one in the area, reaching 120 meters; the “Blue Abyss” goes down to 80 meters and the “Black Hole” has a maximum depth of 60 meters. These are just three places which drop down to bigger depths, within 208 different cave systems, which add up to 910 kilometers of explored cave passages. There are systems which go horizontally for kilometers and kilometers and don’t get deeper than 5-8 meters. Now, the average depths here, in the caves, are 14-15 meters. These shallow depths and a lot of other “diver friendly” conditions make it possible to explore these spreading cave systems with crystal clear, warm water and hundreds of entrances. On top of this, the caves are highly decorated with stalactites and stalagmites, their beauty making you want to go again and again!

The cave passages were formed over millions of years, by water searching its way through the limestone, which the Peninsula of Yucatán is made of. But to build the dripstone formations the caves had to be dry. According to scientists the caves have been affected by four ice ages. In these times the ground water level was much deeper and you were able to walk through the caves; the rain water seeped through the ceiling of the caves dissolving calcite out of the limestone. When the rain water dripped out of the ceiling of the cave, it evaporated and formed stalactites from the ceiling and stalagmites from the floor. Some other caves have little dripstone formations, but, as they are quite corroded, they look very bizarre just like you would imagine the landscape on the Moon.     

Which is your favorite dive spot (cave, reef etc.)?

Sac Actun cave system.

Do you have any special preparations/rituals before these exploration dives?

Not more than checking my dive gear systematically for function!

Which is your favorite configuration/equipment to use when cave diving?

Definitely sidemount configuration! It’s more efficient and safer!

Do you dive on air or gas mixes?

I use Nitrox most of the times, just for safety. Dive profiles in cave diving are usually odd! Up and down just like the cave wants it, this is how you have to go!

How dangerous is cave diving? Which is the most important safety rule when exploring caves?

Cave diving in general is very dangerous, when people enter the caves, not knowing what they are doing. If untrained (cave training) divers enter a water-filled cave, there is a bigger chance that they will stay in there, than they will come back! But with good training and the right attitude cave diving can be done very safely!

Which is the minimum certification level you need for cave diving?

For safe cave diving, people need to become “Full Cave Diver”.

You have a diving center, Xibalba Dive Center, opened since 7 years ago and we presume you meet lots of people interested in discovering the underwater beauty of caves. In your experience, is there something particularly difficult (a particular problem) for those seeking certifications in this field? Is cave diving for everyone?

No, cave diving is not for everyone! The first thing is the diver really needs to have the wish to dive into a water-filled cave! Any other reason why people start to cave dive – “because friends do it” or “because tech diving is cool” and “look at me, how much gear I can handle at one time” – that’s all wrong! And it is unsafe if people enter caves for reasons like that. Individuals which can take responsibility for themselves and have some common sense, usually know if it’s a good idea for them to start this course or not. People which started the cave course out of the wrong reasons or with a wrong idea about cave diving usually find out during the course and are normally not able to pass.

What are your plans for the future? Any particular cave/dive site you’d like to explore?

What I would like to do is try to raise awareness to these caves and the aquifer of the Peninsula of Yucatán. The caves are just wonderful and just their beauty makes it totally worth it to protect them. But even more! These caves are a treasure for science! Geology, hydrology, paleontology, archaeology, anthropology! Where “geo” and hydrology are a bit dry stuff, “paleo”, “archaeo” and anthropology are very interesting topics even for the public.

During our explorations we find a lot of remains from classic Maya periods or even older from the last ice age. Explorers have found all kinds of mega fauna, like: giant sloth, mastodon, different carnivores and… humans from the last ice age! Those humans are the oldest remains found in all the Americas. These oldest remains found so far south make the scientists consider rethinking the theory on how humans came to the Americas. As well, the shape of the skulls let them think that the first Americans came from a different regional provenance than thought so far.

But raising awareness for these caves is not easy! Because people can’t see them! It is easier to protect the last panda bears, because they are so “sweet”, but almost impossible to protect the ozone, because it’s invisible and therefore people don’t care! It’s similar with the caves! They are out of sight for most people, so they don’t care.

With further explorations, articles like the one we are writing right now and a documentary which we are doing right now, we try to make the caves “visible” for the public. The awareness we are trying to get is extremely needed, because the aquifer of the peninsula is in great danger. The caves and actually the whole rock matrix are saturated with water! Salt water below and a relatively thin fresh water lens on top. This fresh water lens still could be Mexico’s largest fresh water reservoir, with drinking water quality! This water is about to be wasted by too much population living on top of the caves and the quick growing tourism in the Riviera Maya. Waste water needs to be treated extra carefully here and development needs to be restricted, if we would like to give the caves, the water and lots of uncovered discoveries a future!  


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4 responses to “Exploring Earth’s insides: cave diving in Mexico”

  1. cristina says:

    17 Mar 2011 at 23:52


  2. marlien colina says:

    20 Mar 2011 at 12:15

    Diving is a passion. To enjoy the beauty under the sea. To be surrounded by thousands of fishes as if they trying to tell you smething.
    Would love to explore the caves. Let me know which time of the year is the best time to do it.
    best regards

  3. Well, from the top of our heads we would say that you can cave dive all year round. But then it depends where, in which area you would like to go cave diving: there are some places where you have to take into account the flooding of the caves due to the rainy season, which, among other things, has as a result a low visibility in the water. If we talk about the Yucatán Peninsula, there you don’t have this problem, so all you have to think about is the best time that suits you.

    Enjoy your diving adventures!

  4. Agassi says:

    08 Apr 2011 at 01:18

    wish i could be there & doing that :( well done sis :)

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