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Zen and the Art of Mexican Cave Navigation

Do you know your arrows, cookies, REMS, TEMS, presence, personal and team markers? Singley or in combination? Jump protocols? If your answer to any of these is ‘Nada’ you may find yourself lost in a Mexican cave. Fortunately, underground explorer and instructor Natalie Gibb has agreed to provide safe navigation through the watery wilds of Riviera Maya. Grab your markers.

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Photos and text by Natalie Gibb

The most idiotic cave navigation mistake I ever witnessed happened on a dive in Cenote Chan Hol about eight years ago. Exiting the cave, my buddy and I approached our jump line, but were pushed out of the way by a solo diver who elbowed his way over our jump line and into the side passageway. 

I stared in disbelief: the diver had not installed his own jump spool, he had just swum over mine. Had he even noticed my jump spool? Did he realize he was swimming into a side passageway? My buddy and I both had personal markers on the main line, as well as markers on our spool. My jump spool had a neon green line, and all of our markers were clearly marked with reflective tape and our names. It was not subtle.

I signaled with my light to the solo diver, and gestured, That’s my jump! He shrugged nonchalantly, turned around, swam back over my jump spool to the main line, and trundled on down the principal cave passage. If I hadn’t had a regulator in my mouth, my jaw would have dropped open. 

Since that day, I have viewed cave navigation in Mexico as a two-part responsibility: 

  1. Don’t confuse yourself or your teammates.
  2. Don’t confuse other divers. 

As one can imagine, the latter is the more difficult to accomplish. 

Cave Training Agency Differences vs Regional Navigation Differences

This article began as a comparison between different cave training agencies’ navigational standards. Interestingly, there is not much to compare!   From my research it seems that TDI, IANTD, NSS-CDS, RAID, PSAI, and GUE agree on a basic philosophy: specific navigational markings and protocols are often region-specific and even cave-specific. Every instructor from every training agency I have spoken with has stated more or less the same thing: While agencies may have general guidelines, navigation procedures are left up to the instructor. 

As a TDI instructor, my students have mentioned that it’s frustrating not to have exact navigation protocols written out in the textbook. I can understand their annoyance, but from an instructor’s standpoint, I prefer it this way.  Not having rigid operating procedures published in training manuals allows cave instructors to teach to their local protocols. 

While GUE is perhaps the clearest of all agencies, most training agencies agree on basic best practices, including the need to use personal markers to mark the exit side of intersections, the acceptance of cookies as a navigation tool, and the need to maintain a continuous guideline to the open water by using jump spools and reels. 

If regional peculiarities, as opposed to dogmatic navigation standards, dictate protocols, the question becomes: What makes Mexico cave navigation different? How should you navigate there? 

What Makes the Caves in Mexico So Confusing?

Several factors make the navigation in Mexico challenging. I believe one of the major factors is that Mexican caves usually lack strong flow. Divers who have grown up navigating caves in other regions are often used to the orienting movement of the water, providing a physical sense of directionality; it’s unlikely to become truly confused about your direction of exit if the water is pushing you “out.” Of course, there are exceptions to this rule, but in general I find noticeable flow is an excellent, almost subconscious indicator of directionality, and it’s missing in most Mexican caves. 

Diver Stephanie Lee hovers between two massive columns at Cenote Nai Tucha. Mexican cave systems can be very complex and many cenotes cannot be used as exits.

The cave systems in Mexico are very complex, with multiple cenote entrances and exits. This may sound like a benefit, but in reality, it’s not possible to exit the water in all of the cenotes, and even if you can get out of the water, you could find yourself deep in the jungle without a road or the ability to call for help. Several years ago, a lost diver perished from exhaustion after blindly following the cave arrows to an alternate exit, then wandering lost in the strong jungle heat. 

Nicholas Wheeler inside the cave Nohoch Nah Chich. Mexican cave navigation often follows its own logic that can be confusing to divers unfamiliar with the system.

The arrows in Mexico’s caves are likely to alter directions throughout a single dive, changing to indicate whatever the person who placed the arrows felt was the nearest surface or exit. That person could have been wrong. The route to the “nearer entrances” might involve 16 jumps and a no-mount restriction. The lines could have been cut or changed since the arrows were placed. There are no warnings, and there is no system in place, although we are working on one!

Additionally, Mexican cave navigation follows its own logic, different from that of other regions. We use multiple arrows, directional changes, and pretty much zero distance markers. Areas far back in the cave, or areas that were explored in past decades, may have “reach gaps,” often unmarked jumps that end centimeters from the main line, as well as blind T’s, and other navigational monstrosities. My favorite recent bizarre navigation find was an “H” intersection. 

Don’t Depend on the Arrows! 

It’s best to view cave lines and arrows as secondary navigational tools. What’s your primary navigational tool? The cave itself. 

Joe Fellows at Cenote Nohoch Nah Chich. Instead of relying solely on the line, compare your compass with the expected general heading.

Plan this out ahead of time if you have a map, and confirm it during the dive by looking back and actually checking your compass once you have completed a jump or T. If you know your directions, you won’t have to rely on the pesky arrows. The magnetic field of the earth is unlikely to change during a single dive. In a pinch, caves north of Chan Hol Cenote are typically upstream to the northwest and downstream to the southeast. This changes a bit south of Chan Hol, due to fracture zones. 

Cave tunnels often have a general direction, even if they twist and turn a little. Carry a compass and keep track of which direction you are traveling, in many places it is more or less uniform throughout the dive. You don’t need a degree heading; northwest-ish in and southeast-ish out will be enough to determine your exit direction if you get confused. If you make a 90 degree turn, you should notice the heading change. If you make a jump off the mainline or navigate a T intersection, it’s essential to know the exit direction along the mainline once you return to that point. 

Nicholas White in a tunnel towards Cenote Coop One. Despite some twists and turns, cave passages often follow a general direction.

Natural navigation is also important. A diver can observe many key features of a cave without a doctorate in hydrogeology. Is the cave big and wide, or small and restricted? What color is the floor sediment? Are there any unusual speleothems that catch your eye? Do you feel water flow? Was there a major depth change? Maybe you swam over a collapse? If you swam into the cave through a small, restricted tunnel, and you turned around to exit but passed no restrictions, you are going the wrong way.  

This simple observation would have saved multiple dive teams who all made the same mistake. They entered Cenote Kalimba and made a jump from an arrow pointing away from their exit towards Grand Cenote. When they retrieved the jump spool, they swam toward Grand Cenote instead of Kalimba, through enormous cave passages instead of restrictions. They blindly followed the jump arrow, which was not pointing toward their exit; they did not correct themselves,  though the cave passageway they were in was very different from the cave passageway leading to their original exit. The more you can learn about geology, the easier it is to read a cave, remember it,  and notice if you are going the wrong way.

Alex Buess at Santuario de los Guerreros. Enourmous and numerous cave passages can easily be misleading.

Mexican System Markers

Of course, lines and arrows are important to understand, and they give divers information about the general layout of the cave. While there is no standardized system of marking cave lines in Mexico, most caves follow a somewhat logical method. Again, a diver should never assume that the arrows are actually correct or that exits indicated by the arrows are accessible. 

A single arrow usually indicates the presence of a jump line.

In Mexico, jump lines are usually indicated by a single arrow on the main cave line. This is different from Florida, where jumps are often marked with two arrows (a double arrow). Interestingly, double arrow jumps do exist in Mexico, but they are rare and have a special significance – they indicate a particularly important jump, such as a jump to complete a circuit or a traverse. Divers familiar with popular Mexican caves may have noticed this in the double arrow jump to the Death Arrow Passage in Cenote Maya Blue, or the double arrow jump to complete the circuit in Cenote Minotauro. 

Double arrows are less common, and indicate a significant jump.

There are also a great number of secret or hidden jumps that are not marked at all on the mainline. Examples include the jump to the Chinese Garden at Cenote Tajma Ha, or the jump to the Room of Tears in Cenote Carwash. 

From a practical standpoint, the lack of double arrow jumps means that line-to-line jump connections are generally not used in Mexico, and a better protocol is to tie into a line marker (more on this to follow.)

Opposing arrows suggest there are equidistant exits in both directions.

As mentioned above, arrows will often change directions along a single cave line. If you swim far enough into a Mexican cave, it is common to encounter a set of two arrows pointing in different directions. These are commonly referred to as a directional change or opposing arrows. The purpose of opposing arrows is to indicate that there is an exit equidistant in each direction, and to draw the diver’s attention to the fact that the line markers past the opposing arrows will point away from the diver’s original exit.

A pack of three arrows suggests exits in both directions, with the doubles arrows indicating the closer exit. 

Similarly, a set of three arrows, with two pointing in one direction and one pointing in the opposite direction is intended to indicate two exits, with one being closer in time or distance. However, keep in mind that system arrows may also flip direction without opposing arrows as a warning. It’s your job to notice this.  Common practice is to leave a line marker (cookie or REM) on your team’s exit side of the opposing arrows or first flipped arrow to confirm your direction of exit.  

T Intersections. T intersections are generally rare in Mexico. Most navigation is accomplished with jump lines or gaps. T’s are most often present at major intersections, when the cave splits into two equally sized tunnels. At a T, one or more exits are indicated by system arrows pointing away from the T toward the exit.  T’s are also common close to cenote entrances, with a double arrow indicating the presence of a cenote off the main tunnel.  As with opposing arrows,  good practice in Mexico is for the cave team to mark their exit side of the T with a personal marker. 

A T Intersection with an arrow indicating a single exit. 
A T Intersection with arrows marking two exits. The double arrows most likely indicate a nearby cenote.

At this point, an important clarification must be made: never blindly follow system arrows toward an exit that you have not personally confirmed. Cave arrows may point toward an exit that requires multiple jumps, a no-mount restriction, or that is blocked by a collapse that occurred after the original line was laid.  Sometimes line markers are simply wrong. Always return to your original proven exit regardless of the arrow direction, and you will stay safe.  

Personal Markers

Three main types of personal markers are commonly used in Mexico cave diving, and many divers now 3D print or craft their own, very unique styles.  The most common markers are Arrows, Cookies, and REMs (referencing exit markers).  It’s important to consider directionality of personal markers and where in the cave they can be used.  

Arrows. Personal arrows are commonly used to anchor jump spools. However there are a few situations in which I feel that arrows should not be used. In accordance with Rule #2: don’t confuse other divers, it’s generally frowned upon to place personal arrows directly next to system/permanent arrows. A personal arrow, no matter how nicely marked, may look like a system marker to another, less observant dive team, and placing a personal arrow very close to a system marker may lead other divers to believe a double arrow is present. Remember, double arrows have a special significance in Mexico. 

At jumps, placing a personal jump arrow within a few inches of a system arrow can make it look like a double arrow jump.  Instead, the team should separate the personal jump arrows from system arrows by 0.5m/1.6 ft (if possible) to avoid confusion. 

Placing a personal arrow next to a jump arrow may create navigation that looks like a double arrow jump.
Marking a T Intersection with a personal arrow may lead to other teams confusing the personal arrow for permanent navigation.

At T-intersections or directional changes, using a personal arrow to mark the team’s exit may confuse other teams, as it may look like a double arrow indicating a nearer exit. For these applications cookies or REMs are preferred.  

Cookies can be used to mark a team’s exit at a T Intersection.

Cookies. Cookies were a Mexican cave diving innovation invented by explorer/instructor Daniel Riorden in the late 1990s, in accordance with Rule #2.  Cookies are round, or non-directional, and are typically not used as system markers. The shape makes them clearly personal markers, which simplifies marking intersections and directional changes as all other cave teams know that a cookie indicates nothing about general cave navigation. Cookies may also be used to mark a cave team’s reels. 

Cookies may be used to mark an arrow pointing away from the team’s exit, by placing the cookie on the exit side (in this case right).

Cookies are appropriate for most uses, with the exception of anchoring jump reels or spools. It’s inappropriate to tie a reel or jump spool onto a lone cookie, as the cookie alone does not indicate a direction of exit at the intersection, a clear violation of Rule #1: Don’t Confuse Yourself or Your Team Mates. 

REMs. REMs (Referencing Exit Markers), invented by Bil Phillips, are a common sight in Mexico and uncommon in most other regions.  They are rectangular markers, with slats for line attachment closer to one end. The longer end points towards the team exit.  

REMs are rectangular personal markers. The longer end of the REM faces out.

REMs are interesting in that they are directional,  but can not be confused with arrows. They can be used for the same functions as both arrows and cookies, eliminating the need for a diver to carry a variety of personal markers. In my conversations with Bil, he told me this was not his original intention for the markers, but he liked that people were getting creative with them.

REMs have one other useful feature, which is that the exit side of the marker has enough space to write a serious note. This can be left on the line for notes to a buddy or for personal notes, in place of wetnote pages or other methods. 

Creating Your Personal Markers

No matter what style of markers a diver chooses to use, their markers should be clearly personalized. All organizations teach divers to write their names, nicknames, or an identifying word on their personal markers to indicate who the marker belongs to. This helps to fulfill both Rule #1 and Rule #2, making the markers easy to identify. 

An additional method of personalizing cave markers that I recommend is to make them touch contact identifiable. I ask my divers to modify their markers in a way to make them uniquely identifiable in zero visibility, such as cutting a corner off, punching holes in them, or adding something as simple as a cable tie in order to physically identify them if visibility is lost. 

Many divers also like to number their markers, which allows divers to account for all markers and refer to a certain navigational decision in the debriefing or in their notes – for example, “the jump where the diver put down marker number three.” 

Exploration markers are typically arrows, and may have the exploration teams info, date of exploration, and a key word or identifying number written in them.

A word of caution here – it is possible that some system or permanent markers have a diver’s or dive team’s name on it. These are exploration markers. They typically have the team’s names, the date or year of the project, and maybe even a keyword or number written on them, and are not marked with touch or physical identification cues. Exploration markers are so much fun to find! Every time I run across a historic marker with an explorer’s name on it, I feel a kinship to the original explorers and imagine what the person must have felt like, being the first human in this cave. If a diver has a question about the cave, the presence of the explorer’s name indicates who to contact with questions. 

Team vs Individual Markers

Now we are getting into the great debate! Which is better, team or individual markers? 

With the “team marker” approach, the team leader places a single cookie or REM on the exit side of a T. 

When cave divers are using the team marker approach, the diver in the front of the team places all markers for the team, marking and placing jump lines, marking T’s, and placing any other markers that are deemed necessary. Other team members carefully observe the diver in front, and confirm that the markers are correctly placed. The advantage of this style of marking lines is that there are fewer markers on the line, and that it is slightly faster than having each diver personally mark intersections. UTD’s Andrew Georgitisis rather infamously premiered a REM-style “TEM (Team Exit Marker)” in a Facebook video last year advocating the use of team markers.

With the “individual marker” approach, the each diver places a cookie or REM to mark the exit side of a T. 

If a cave team uses the individual marker approach, each diver places a personal marker to mark the team’s exit at every point of navigation, including jumps, T’s, and directional changes.  The advantages of this system are that each diver physically participates in the cave navigation, which helps to fix it in his or her memory. Additionally, more markers are easier to see, and add an additional degree of personalization to the navigation. If my team is using all REMs, and your team is using arrows and cookies, just the fact that a jump is marked with arrows and cookies means that it is not mine. 

When jumping from a team marker, the team leader places the navigation and all others confirm it is correct. 
When jumping using “individual” markers, all team members mark the exit side of the jump.

However, the most important argument for this method, is that individual markers create a level of redundancy in navigation. If a diver accidentally ties into a jump arrow that points away from the team’s exit (and no one notices), but the other divers mark the exit side of the intersection correctly with their cookies or REMs, it is clear that there is a navigational discrepancy upon exit. Divers then know to refer to their compasses and natural navigation clues to determine the correct direction to exit, instead of blindly following the arrow in the wrong direction when leaving the cave. This can be life saving. GUE uses this approach, though most training organizations do not state a preference.

Individual line marking procedures can highlight discrepancies in line marking, allowing divers to notice an error and take appropriate action.  Here, the arrow is pointing away from the team’s exit, but they marked the intersection properly.

Finally, some instructors teach that in an instance of team separation, divers leaving the cave remove their personal markers, while leaving the jump lines and other team member’s markers in place. This indicates to the team who is still in the cave, and who has made it out. This method of dealing with a team separation is debated in the cave community. 

The advantages of individual markers as far as clarity, redundancy, and problem solving make the individual marker method my choice.

Presence Markers

Presence markers are personal markers that are placed at the beginning of a cave line when the line starts in open water and no primary reel is required, or on the primary reel line when a reel is run from the open water. Presence markers can be team markers or individual markers, and indicate the presence of the team in the cave. When individual presence markers are used, they additionally indicate the number of divers in the cave. 

Individual presence markers at the beginning of a cave line.

If a team must exit in complete zero visibility all the way to the end of line in the open water, personalized presence markers allow the divers to confirm that they have navigated correctly to the open water and may safely surface. No agencies seem to have a firm stance on presence markers, nor is this an established local protocol in Mexico. However, I quite like presence markers and use them in my courses and personal diving. 

Jump Protocols

When cave divers swim from the main cave line to a secondary line (jump line) in a side passage, they have made a jump. As all modern training organizations require cave divers to maintain a continuous guideline to the open water,  the cave teams install a jump reel or spool to connect the mainline to the secondary line. This is a visual reference upon exit and allows the team to navigate out of the cave in zero visibility by touch. 

How should a team install a jump line? Good question! Once again there are many options, and again, there is no “right” answer as long as the marking is clear to other divers, the team that installed the line, and has some sort of marker indicating the direction of exit. It’s helpful to use colored line on jump spools as opposed to white line, which is typically used for permanent cave lines, as this makes the temporary nature of the line obvious to other teams.  Here is a non-exhaustive list of options. 

Line to line connection. When a team loops a jump spool directly around the cave line (as opposed to tying the spool into a line marker), the jump is a line-to-line connection. This sort of navigation is more commonly observed in Florida and other locations where jumps are indicated by two arrows. The team can tie the jump spool between the two jump arrows without risk of the jump line sliding out of position. Using this method, two arrows are present (if they are pointing in the correct direction) to indicate the team’s direction of exit. 

Line to line connections are common in regions where double arrow jumps are used.

Line to line connections are less common in Mexico, because jumps are usually indicated by single arrows. The jump line can slide around without arrows blocking it on each side.

In Mexico, where jumps are indicated by a single arrow which may be pointing away from the team’s exit, this method is generally frowned upon. Lines that are not anchored by a line marker are likely to slide out of position, particularly in zero visibility. 

Jump from a system or permanent marker.  One common method of installing a jump line in Mexico is to loop the jump spool’s line around the system arrow. This fixes the jump spool’s line in place and avoids the problems mentioned above. However, it is important that the team carefully observes the arrow’s direction. Divers should never attach a jump spool to an arrow that points away from the team’s exit. Doing so has been implicated in numerous fatalities, including several well-known accidents at Cenote Kalimba. If the team chooses to use individual markers, team members place cookies or REMs on the exit side of the intersection created by the mainline and jump line. Jumping from a system marker is not possible when the arrow has already been used by another team, or if the jump is unmarked, and it’s a terrible idea if the arrow points away from the team’s exit. Always be prepared to use the final jump method.

Jumping from a system arrow using the team marking approach.
Jumping from a system arrow using individual marking with REMS (cookies may also be used).

When jumping from a team personal marker, the leader installs his own arrow or REM on the line.

Jump from a personal marker.  To jump from a personal marker, the team leader places an arrow or REM on the line indicating the team’s exit direction, and ties into the personal marker. If individual markers are used, each member of the team places a cookie or REM on the exit side of the intersection created by the jump spool line and the main line. Again, this can be used as standard protocol, in the case where the jump arrow is pointing away from the team’s exit, in the case where the arrow is already used by another team, or in the case where the jump is not marked by a system or permanent arrow. This is my preferred method because it avoids uncertainty, and I use the same exact protocol for every jump, regardless of what is present in the cave. 

When jumping from an individual personal marker, the leader ties into his own arrow or REM, and all team members mark the exit side of the intersection with personal markers.

If a team chooses to jump from a personal marker when a system arrow is present, what side of the system arrow should the team jump from? I prefer to install my personal marker at least arm’s length away from the system arrow to differentiate my navigation from the system navigation. I like to jump from behind, or from the cave side of the direction the system arrow points, because this leaves the permanent marker on the exit side of my intersection, allowing other teams already in the cave who have noticed this arrow to have an unobstructed reference to the exit. 

Marking Reels and Spools. 

When tying into the main cave line or a jump line, many divers, myself included, like to place a marker on the reel or jump spool line. On a primary reel line, these markers serve as presence markers. The markers also help to visually and physically identify the diver’s line in zero visibility, especially in the event that there are multiple spools or reels tied into the cave line. Finally, this helps to unambiguously identify similar types of spools and reels, helping to avoid  removing a different team’s reel or spool by mistake. Not everyone does this, and some consider it redundant and unnecessary, as realistically divers should be able to identify their own reel or spool. I feel like it is extra clear, so I like to mark my spools and reels. 

A spool is marked with a team cookie.
A spool is marked with individual REMs.

Navigating Around Multiple Cave Teams

Placing a jump as the second team in the cave (yellow line with cookies and arrows).

A brief note is warranted to mention protocols for navigating when there are multiple teams in the cave.  The general rule is to attach any spools or reels cave side of another team’s spools, unless there is a very large space exit side.  The same rule applies to the placement of jump spools. When navigating a T, place your markers on the exit side of the other teams markers, so that their markers are the first encountered during the exit. 

Tying into a cave line or jump line as the second team (yellow line with cookies and arrows).

What’s the Number One Navigational Mistake I Should Avoid as a Tourist Cave Diver in Mexico?

The number one navigational mistake to avoid is to blindly follow arrows and lines to your death. Nearly every Mexican cave fatality I am aware of involves navigational errors exacerbated by camera use. Mistakes include divers jumping off system markers pointing away from their exit and subsequently going the wrong way when returning from their jump line, or teams getting turned around when taking photos.  Mark all intersections methodically with personal markers, understand the overall compass heading of your planned dive, and be aware that arrows do not always point towards your team’s exit, or even an accessible exit. Notice if arrows change directions and mark them accordingly. In the event that you become confused, use your compass heading and natural navigation in conjunction with the cave lines to find your way home. 

Mexico Cave Navigation Is an Art

Navigation in Mexican caves is subtle and often confusing. My shop teaches the system of navigation that we like the best, but there is a wide variety of protocols used in the area, and I wouldn’t say that any one way is necessarily incorrect. I am probably in the minority with this opinion, but I would say as long as you and your teammates stay oriented, and you don’t confuse other cave diving teams, have at it. No matter what you do, someone else is going to think you are wrong. Chin up. Did you confuse your team? Did you confuse other teams? No? Good enough. 

In fact, I actually think it’s great that there are slight variations in the way people mark their lines. If I use REMs, and you use arrows, then I can easily and quickly identify my markers simply because they are different from yours. Nice! 

Divers Nick, Nik, and Troy turn a corner at Cenote Nohoch Nah Chich. Always be sure to be on the same page as the rest of your team and develop a navigational strategy together.

One cannot be too strict with navigational protocols in Mexico, because while a team can have a standard way of placing and marking lines, the established lines in Mexico do not have standardized systems of marking.  Maybe you like to anchor your jumps on personal markers behind the system markers? I do. But it’s not always possible based on the layout of the cave. You must adapt your navigation to the environment, and that’s why it’s an art! As unsettling as this is to many people, there are no absolutes. 

So Many Options! What to Do?

Yes, it can be confusing, and determining your personal or team navigation style takes some thought and discussion within the dive team. There are options, and as grown up adults, you get to choose what is clearest and easiest for you. When evaluating a navigational method, just make sure it doesn’t violate the rules of safe cave navigation:

  1. Don’t confuse yourself or your team mates.
  2. Don’t confuse other divers. 

Based on the previous discussion and general cave training organization guidelines, we can add two additional points. 

  1. Maintain a continuous line to the open water using spools and reels as needed.
  2. Have a marker on the line indicating your direction of exit at key points of navigation, including jumps, T intersections, and directional changes. 

In addition, I would urge dive teams to be consistent. Come up with a protocol, whether it’s team or individual markers, anchoring your line on system markers or personal markers, and use the same protocol on every dive. This makes in-water decision making easier and helps to avoid confusion. Review your navigational protocol with new team members, and agree to a protocol before entering the water the first time. 

Diver Bre Kramer at Cenote Caterpillar. The cave line can be a good directional tool but at the end of the day the cave itself will give you the best navigational indicators.

No matter what navigational procedure your team chooses to use, keep in mind that while important, plastic markers and the cave line are secondary navigational clues. Your first source of navigation is the cave itself: directionality, formations, physical features, and flow if it exists.  Unlike lines, cave features are unlikely to be removed or changed. Learning to observe and read the cave will increase your safety and enjoyment!


Natalie L Gibb’s passion in life is underwater cave exploration and conservation. With her exploration partner Vincent Rouquette-Cathala, she has led her team to discover over 20 previously unknown cave systems in Mexico’s Yucatan Peninsula, mapping more than 80 kilometers/nearly 50 miles of cave passageways. She is a public speaker, author, photographer, and videographer, and a member of the Woman Diver’s Hall of Fame. Natalie is co-owner of Under the Jungle, a cave diver training center in Mexico, and a TDI Full Cave Instructor.

Cave

Meet The British Underground

It’s cold, dark, you can barely see two meters in front of you, and you’re diving alone. Oh, and there’s a sump up ahead. Welcome to the British Underground! Not exactly a scooter-ride in the warm, clear, stalactite studded caves that lay beneath Riviera Maya. Here British caver and training officer for the Somerset Section of the Cave Diving Group Michael Thomas guides us on a tour of British cave diving and explains why it may not be everyone’s cuppa tea.

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by Michael Thomas 

Header photo courtesy Michael Thomas. Diver entering Keld Head in the Yorkshire Dales.

Recently someone approached me about British cave diving wondering what in particular makes it so very different from Mexican cave diving, for example, and why it’s so appealing to a select few. In the U.K. we have two types of underground diving. The first is the significant number of flooded mines that have given rise to some world-class mine diving that’s becoming very popular with technical divers from around the world. The second type of  underground diving is traditional British cave diving, which, due to the nature of U.K. caves, involves both dry caving and cave diving. The aim is to explore the caves underwater or in the dry underground following it as far as possible. We are now finding that technically trained mine and cave divers are starting to learn the art of dry cave exploration in order to further their knowledge and adventure, some even gaining enough experience to join the Cave Diving Group in the U.K. 

Firstly, a little about myself if I may be so bold. My diving career is now in its thirty-third consecutive year, from starting out as a trainee open water diver with BSAC to trainee cave diver within the CDG to becoming the Training Officer of the British Cave Diving Group Somerset Section in the U.K. Since 1996 I’ve had links to TDI and currently hold Full Cave Instructor, Sidemount and Tech Instructor status with TDI, active mod 3 CCR cave diver, and on the British Cave Rescue call out list as a diver. 

My diving life crosses all paths of British and worldwide diving, from open water to cave and tech. I’m actively involved with technical diving conferences and a fellow of the Royal Geographic Society of the U.K. My father was a cave explorer before me, and my son has also taken the same path. You could say, caves and diving are our lives. 

See The CDG 

To understand British cave diving we first need to understand the CDG.  The Cave Diving Group is the representative body for cave divers in Great Britain and Northern Ireland and is a constituent body of the British Caving Association (BCA). Its function is to educate and support cavers for recreational and exploratory operations in British sumps. The CDG also helps control access to numerous cave sites, including Wookey Hole and Gough’s Cave  in Somerset, and Keld Head And Hurtle Pot in Yorkshire, in conjunction with the BCA. The group was formed in 1946 by the late Graham Balcombe, and its continuous existence to the present day makes it the oldest amateur technical and cave diving organization in the world. Graham Balcombe arguably invented cave diving in the U.K. with his audacious dives in Swildon’s Hole cave and Wookey Hole cave in 1935. 

Now the huge difference between the Cave Diving Group and other cave diving training agencies is you can’t just sign up and pay to do a training course. From the very start in 1946, the prerequisite for joining the CDG was always and is a knowledge and experience base of dry caving skills, though in modern years we also require an open water certification. Once you have made yourself known to one of the four sections that make up the CDG—Somerset, Welsh, Northern, and Derbyshire—and proven you have dry caving skills and can get along with your new-found friends, you are voted in, hopefully to whichever section you approached. 

CDG rescue practice exercise after the Thailand rescue to update our rescue skills and standards. Photo courtesy of Michael Thomas.

As a trainee member of the cave diving group, the training is apprenticeship based and generally takes between 12-18 months. At the end of that, a written exam and an underwater test is completed, and as long as your section is in agreement, the qualified diver status is awarded. It’s a slow process but ensures adequate experience is gained in a variety of different sites and conditions, producing a cave diver that is capable of exploration cave diving, rescue work, and continued training of new members. 



The Solo Mentality 

Probably the one difference with most U.K. cave diving, that is a world away from agency standards, is the CDG approach to team diving. In all but a few sites in the U.K., the CDG considers solo diving the safest way to approach the dive. While divers might enter the cave together as a team, and dry cave their way to the dive base (dive site within the cave), once they are in the water they typically dive solo. This is because a diver is usually unable to help another diver in the water. Then they meet up on the other side if more dry caving is to be done. 

CDG trainee divers are taught from the beginning to be solo divers or work within a team as solo divers, something we call “team solo.” Most dive sites in natural caves in the U.K. are unsuitable for team diving. The few sites that are suitable for a team to operate together, such as Wookey Hole in Somerset, Hurtle Pot in the Yorkshire Dales, and Porth Yr Ogof in South Wales, should really be a team of only two divers. Passage size and visibility generally means divers can’t see the third team member if at the back or front of the team. The mine diving sites are much more suited to team diving with larger passages and clearer water. The links below offer more information on mine diving in the U.K. [Ed.note: Global Underwater Explorers does not sanction solo diving.]

Robert Thomas at Top waterfall sump dive base Ogof Ffynnon Ddu Cave Wales UK. Photo courtesy of Michael Thomas.

The article, “Solo Cave Diving,” on the CDG website explains why it recommends solo cave diving as the safer alternative for U.K. sump conditions. It lists some of the advantages of solo cave diving as follows:

  • There’s no one to get physically jammed in the passage behind you (thereby blocking your exit).
  • There’s no one behind you who may get tangled in the line and have to cut it—leaving you with no guide home.
  • There’s no one to accidentally disturb your ‘out tags’ at line junctions (e.g. in one cave there are 10 branch lines off the main line in the first 500 m/1640 ft of passage).
  • There’s no one to cause silt problems (but yourself).
  • There’s no chance of being called upon to share air—in small passages.
  • There’s nothing to get confused about—communication in sumps varies from difficult to impossible.
  • There’s no one to provide you with a false sense of security.
  • There’s no one to worry about but yourself, so you can concentrate on your own safety.

Equipment Configuration

Due to the generally small passage size of British caves and the sometimes energetic nature of transporting equipment to a cave dive base (station), sidemount diving is the normal equipment configuration. Sidemount started in the U.K. in the 1960s with a need for streamlined and lightweight diving equipment. U.K. cave divers today will have a choice of sidemount harness for the project they are involved with. In a short, shallow, or constricted dive, the diver will use a wetsuit and a lightweight, webbing-only harness with no buoyancy, as it’s not needed if your chest is on the floor and your back on the ceiling. 

 Diver leaving Dire Straits dive base Gough’s Cave Somerset UK. Photo courtesy of Michael Thomas.

In slightly larger cave passages, the modern British cave diver will use one of the now-common sidemount harnesses that are available. Many British caves require vertical cave techniques to reach the water, so the divers have modified the sidemount harness to be able to descend into the dry cave, do the dive, and then climb out. It’s very rare to find a British cave diver with an unmodified sidemount harness. For exposure suits, many short dives and some longer dives, if significant dry caving is expected before or after, the dive will be done in a wetsuit even though water temperature is on average between 7-10 degrees C/45-50 degrees F. This is for practical reasons, as it’s very difficult and potentially dangerous caving in a drysuit, so better to be slightly chilly during the dive and caving safely. 

For larger sites and when the diver is expected to be underwater most of the time, a drysuit is sometimes carried to the dive base and put on underground, to be utilized for the dive. As most divers are solo diving, having two short standard-length hoses on their regulators is normal, although for team diving or cave rescue, a standard long hose is used on the right. 

British cave divers always use helmets, as they provide protection from the environment in the dry caves as well as underwater, and are a great place to carry lights. Hand-held primary lights are used in larger, clearer passages with the helmet lights in reserve. For dive lines, we use 4 mm thick lines as permanent dive lines and we have fixed junctions in all caves— no jumps or gaps. Standard line arrows and cookies will not fit on a U.K. line. Pegs are used, or permanent markers on junctions to show the way home. It’s very unlikely you will see another dive team in the cave on the day you are visiting, and following a thicker line in sometimes low visibility and cold water is much safer and more comforting than trying to follow a technical diving line. 

Exploring U.K. caves 

The raison d’etre for the Cave Diving Groups formation was and still is the exploration of caves, including the surveying and reporting of that exploration and the training of new divers. The CDG publishes a journal four times a year with exploration reports and many books on the subject of U.K. caves and techniques. If it’s not surveyed and reported, it’s not explored. Now, it would be extremely tedious to the reader if I listed all exploration in underwater caves in the U.K.—we have thousands of reports—so I’ll mention a few of the classics to set the scene, and remember all exploration can be researched in the CDG journals. 

If visiting, most U.K. cave divers are happy to show you around or even get you involved in projects, although they will be of a very different style of exploration than found in Bahamas or Mexico, for instance, where swimming into hundreds of metres of new cave is possible. Big breakthroughs in the U.K. are rare, and if a diver explores 10 m/33 ft of new cave with ongoing passage seen, they will be happy. 

Wookey Hole Cave Somerset, Somerset 

Exploration in the home of British cave diving started in 1935 and carries on to this day. Slow and determined work by some of the great names in cave diving, including Balcombe, Martyn Farr, Rob Parker, Rick Stanton, and John Volanthen have seen this multi sump cave reach 90 m/294 ft depth beyond chamber 25 in extremely committing passages. Smaller side passages throughout the cave are still being explored. 

Michael Thomas surfacing in Wookey Hole after Recovering a 3rd 4th Century Roman pot ! Photo courtesy of Michael Thomas.

The Llangattock Cave Systems, South Wales 

Under Llangattock mountain lies many kilometers of caving—two caves, Ogof Daren Cilau at 27 km long and next door Ogof Agen Allwedd at 32.5 km, provide access to many cave diving sites that have provided incredible exploration over the years and will hopefully provide more in the years to come. One of the longest dives in the system is the Pwll y Cwm resurgence at 630 m/2066 ft long, surfacing in the downstream end of Daren Cilau. 

Kingsdale Master Cave and Keld Head, Yorkshire Dales 

One of the true classics of world class cave diving is the Kingsdale to Keld Head system. Graham Balcombe, of Wookey Hole fame, conducted dives in 1945 in Keld Head, and in 1978, Geoff Yeadon and Oliver Statham broke the world record with an 1829 m/6000 ft dive between Kingsdale Master Cave and Keld Head, connecting the two caves. In 1991, the underwater system was further extended, linking it into King Pot cave access to the valley floor, a traverse of 3 km in British conditions. Today, divers continue to explore and extend this system. 

Speedwell Cavern Main Rising, Derbyshire Dales 

This dive site requires a reasonable amount of dry caving effort to reach the dive base. The dive itself is multi-profile with a descent to 36 m/118 ft then up to 2.5 m/8 ft via a constricted rift, then finally down to 71 m/232 ft at the end. In the 1980s John Cordingley and Russel Carter worked the site and finally, 71 m/233 ft was reached by Martin Groves in 2002. The way on was lost in boulders and boiling sand with the water surging upwards. This was confirmed by John Volanthen in 2006. A change in geology and future technologies await. 

The Green Holes of Doolin, Ireland 

In the years leading up to the 1980s, open water divers reported cave entrances in the sea on the Doolin coast. These completely submerged caves are extremely weather dependent due to taking the full force of the Atlantic Ocean. But after experience gained in the Bahamas’ Blue Holes, British divers tried their luck exploring what became known as Green Holes. Several sites including Reef Caves, Hell Complex, Urchin Cave, and the longest Mermaid’s Hole have had successive and continued exploration. 1025 m/3350 ft penetration being reached in Mermaid’s Hole by Artur Kozlowski. Exploration continues when the weather allows. 

Robert Thomas demonstrates vertical caving skills needed to reach many cave diving sites in the UK. Photo courtesy of Michael Thomas.

Swildon’s Hole Cave, Somerset 

A true classic sump diver’s cave with long sections of active wet streamway takes the visitor down to a series of eight short sumps that require diving and more caving to reach the terminal sump and end of the cave at Swildon’s 12. Wetsuits and lightweight sidemount harness and small cylinders needed. A grand day out. 

Porth Yr Ogof Cave, South Wales 

One of the finest and reasonably easy physical-access cave dives in the U.K. The dive starts from a small pool after a short climb down between boulders. A shallow and comfortable passage winds its way up the valley passing Rawlbolt Airbell 150 m/492 ft from base and Four Ways airbell around 200 m/656 ft from base. At 250 m/820 ft from base, a cobble squeeze can be passed to the surface in the dry upper cave. The flow in this cave can be very high and the passage size varies from 1 m wide to 3 m wide, making progress upstream interesting and downstream on the return exciting. 

Hurtle Pot, Yorkshire Dales 

Probably the most dived cave in the U.K. due to its easy access and the possibility of longer dives upstream in a large passage towards Jingle Pot Cave and an area called The Deep reaching 35 m/114 ft depth in a low complicated passage towards the end around 460 m/1508 ft from base. Downstream a 400 m/1312 ft long traverse can be made to surface in Midge Hole cave reaching 20 m/65 ft depth on the way. This cave floods dramatically in bad weather, and constant line repairs need to be made by local CDG divers. 

Peak Cavern, Derbyshire Dales 

Peak Cavern is an extensive dry cave with several significant cave diving sites located within the system. The resurgence is a classic training dive in a lovely bedding plane style passage reaching the surface in the main cave. Ink sump within the cave, nearly 200 m/653 ft long, leads to Doom’s Retreat, an area worked by Jim Lister and the most extensive digging project to find a new cave beyond a sump in the U.K. Far Sump at 385 m/1263 ft long leads to an extensive dry section of cave with some extremely technical caving that can now get you to surface on the hills above. 

Pollatoomary Resurgence, Ireland 

Not many easy surface access cave diving sites that go deep are to be found in the British Isles, but this one in Ireland is one. A resurgence site that reaches 103 m/336 ft but in dark, unfriendly waters. Original exploration by Martyn Farr in 1978 and taken to 103 m by Artur Kozlowski. 

Divers leaving surface in Wookey Hole on a practice cave diving rescue.  photo courtesy of Michael Thomas.

In summary, British cave diving is historically one of the oldest branches of the sport of cave diving. The Cave Diving Group’s knowledge and standards and procedures evolved over the years to the safest method to explore or dive in U.K. style caves. It is not diving in Wakulla Springs and does not pretend to be, although several CDG members got involved in the early Wakulla expeditions. It is at times cold, wet, and unpleasant, but also can be extremely rewarding, with new caves found or just a superb dive in excellent conditions. U.K. style conditions can be found all over the world—think of the Thailand Rescue in 2018—and it’s in these conditions that the CDG system is at its best. If you’re wanting more information on the CDG or sump diving and vertical access sump diving, please give us a shout. Just remember—a pint of English beer is supposed to be warm. Stay safe and dive well. 

Additional Resources:

Website: The British Cave Diving Group

From GUE’s membership magazine QUEST: “British Cave Diving: Wookey Hole and The Cave Diving Group” by Duncan Price

Books about British cave diving:

A Glimmering in Darkness by Graham Balcombe 

The Darkness Beckons by Martyn Farr 

Interview with Cave Diving Legend Martyn Farr

Historical British cave diving films:

Trailer for documentary film ‘Wookey’ by Gavin Newman

The Underground Eiger (1980s)

Articles by Michael Thomas:

Slow Down Young fellas-Attitudes in Technical Diving

The Difference Between Caves and Mines

Mine Diving in the UK


Michael Thomas’s diving career is now in its 33rd consecutive year, from starting out as an open water diver then a trainee cave diver to becoming the Training Officer of the British Cave Diving Group Somerset Section. He is also a Full Cave Instructor, Sidemount and Tech Instructor with TDI, active mod 3 CCR cave diver, and on the British cave rescue call out list as a diver. 

Thomas is heavily involved in U.K. diving projects and training, plus overseas diving and caving. Diving is life or is life diving? 

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