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Incident Report: Lost in a Cave

How could four experienced divers get lost in a cave? Human nature got in the way. Human factors pundit Gareth Lock analyzes the factors that led to this “Oh S***” moment and how they might apply to your diving; they are much more common than you think.



by Gareth Lock

Header photo by Kirill Egorov

A team of four divers, all of whom were at least full cave trained, were exploring a cave system in Croatia. The team had already laid a significant amount of line the previous year, and the plan for this dive was to fix and extend the current line and conduct some basic surveying. They also planned to use a novel camera mount to produce 360-degree imagery using multiple GoPro cameras mounted on a special “selfie stick.” Although the maximum depth was 100 ft/30 m, given the length of dive, they would use twin 18s (18 liter tanks) and a stage and scooters. The cave had a small amount of flow but nothing major.

The dive started as planned, and after 30 minutes or so, the divers reached the end of the line and saw the final tie-off from the previous survey and exploration teams. The lead diver pointed to one of the other three to tie in the exploration reel so that they would be ready to explore once the rest of the team had sorted out the camera gear. Due to the complicated nature of the camera and lighting rig, it had been stowed during the long transit to this point. Assuming that the line was being tied in, the other three busied themselves with sorting out the video gear. This process took them approximately three to five minutes to complete.

Once the video rig was ready to go, the lead diver signalled to the team that they would start exploring the cave and shooting video. At this point, the leader noticed that the main reel, which should have been tied in, was still clipped to the first diver’s harness! And because there was a small amount of flow in the cave, and most of the the team had been fixated on sorting out the video rig, they had drifted from the end of the line and were now in the cave without a fixed line to the surface.

They were now 40 minutes into the dive, 100 ft/30 m deep, and had no idea which way was out. Not a great place to be! The lead diver then started lost line protocols, and it took them 15 minutes before they found the end of the line to tie in to and start their exit.


As with many incidents, it is easy to join the dots and see why the team ended up in the predicament they did. Hindsight affords us a vision that says “it was obvious it would end up like this.” In this particular case, we can easily surmise that the team members were task- focused, they lost” situational awareness, were complacent, made assumptions, and didn’t close their communication loops. However, all of these negative actions regularly happen on other dives but usually don’t result in negative consequences. That is to say that errors are typically only recognized after something goes wrong!

Many times, we don’t even see errors because we aren’t looking for them; plus they don’t create a negative outcome. If we don’t go looking for near misses by reviewing the situation (e.g., by using a structured debrief), we won’t see how the process had errors or violations within it. Consequently, it is the error-producing conditions we need to focus on, not the (positive or negative) outcome. Losing the line is an outcome; why the divers’ attention was pointed at something perceived to be more important or relevant is where we should be looking if we are to improve safety and performance.

In addition to just noticing the outcome, we are hard-wired to focus on the severity of the outcome. The more the severity increases, the more harshly we judge those involved. For example, would our feelings about this event be the same if the team were working in open water and they didn’t remember to tie in and could ascend straight to the surface? And how about if someone had died because they couldn’t find the original tie-off?

So why did this happen? In this case, the task was novel and challenging and was taking a large percentage of the mental capacity of the divers. The diver who was supposed to tie in was likely more interested in the camera, the lighting rig, and the team rather than the primary task of tying in. Although the tying-in task was important, research on brain activity has shown that when not actively directing one’s attention, humans shift focus between four key categories of information: dangerous, interesting, pleasurable, and important (DIPI). In this example, the camera task/rig was interesting (novel activity, part of a project that was pushing the survey) and pleasurable (surveying new cave, shooting 360 video); consequently, “important” and “dangerous” disappeared down the list of things that were considered worthy of the divers’ attention.

Diver Lauren Fanning in Ginnie Springs. Photo by Kirill Egorov.

The lighting team would be focused on configuring their rig, thereby reducing their peripheral vision. Being in a cave with bright lights and being mid-water would reduce it further. Peripheral vision is used to detect movement, and this might explain why they missed drifting further into the cave, and so the danger was missed. Even if they had noticed the movement, the working mental model would have been that the first diver had tied in the line, and there was no cause for concern when they saw that first diver again.

Assumptions and miscommunication are commonplace in modern life. In fact, assumptions are essential to operate at the pace we do, since we are unable to consciously process the vast amounts of information that we receive through our sensory systems. In addition to assumptions, a critical instruction was passed (i.e., tie in the line), but the communications loop was not completed. The leader should have ensured that the tie-in had started before the team began working on the video rig.

Applying these Lessons to Your Diving  

The Limitations of Situational Awareness. If we don’t want to be distracted at the wrong or critical time, we need to understand how our attention system works. We have a finite capacity in our working memory, shown to be seven +/- two elements of information at any one time. Note that this is “elements” and not “pieces” of information, a critical distinction when it comes to improving situational awareness and mental capacity.

As we become more skilled at an activity, we start to chunk information together (e.g., when we first start to dive, we have to actively think about the sequence of activities to stabilize at a stop). These might be: look at the computer/timer, note that we are 3-5 ft/1-2 m below the stop depth, reach back and grab the OPV dump cord (or inflator hose), pull the cord (press the deflate button), monitor how much gas leaves the wing (or the time the button is pressed/cord pulled), and watch the computer to see where we are. Unfortunately, we often don’t get it right, either stopping too soon or too late, and then start to oscillate around the stop depth.

However, when we are more experienced, the activity of arriving at a stop combines all these actions into one “element” that we don’t actively think about, and we get it right the first time. This means we have more capacity to see what else is going on around us and to anticipate what might happen next. The same goes for other technical skills that need to be developed.

Definition of Error. Divers have a vested interest in making sure that they make a decision that ensures that they (or someone else) doesn’t die or get injured. As such, if a diver knows with 100% certainty what the outcome is going to be, and it is a negative outcome, they won’t execute that decision. Errors happen all the time, but not every error ends up as an incident or accident. If we want to improve our safety, we need to invest time to review what we’ve just done and not just the outcome. Ultimately, we need to understand how it made sense for those involved.  

Like incident reports? Read another

Header photo by Kirill Egorov.

Gareth Lock is an OC and CCR technical diver with the personal goal of improving divingsafety and diver performance by enhancing the knowledge, skills, and attitudes towards human factors in diving. Although based in the UK, he runs training and development courses across the globe as well as via his online portal https://www.thehumandiver.com.He is the Director of Risk Management for GUE and has been involved with the organization since 2006 when he completed his Fundamentals class.


Diving Into The Famous Ressel Cave

Belgium service member, cave explorer and tech instructor Kurt Storms takes us for a dive into the Ressel cave system located in Lot. Get out your reels.




By Kurt Storms. Photos courtesy of K. Storms unless noted.

The Lot and The Dordogne areas of France have an abundance of beautiful caves suitable for all levels of diving expertise, situated in glorious rural locations. Sites are mostly found on three rivers: The Dordogne, The Lot, and Célé. The Lot area lies in the northern extremity of the Midi-Pyrenees region, which stretches from the confines of the Dordogne Valley to the highest peaks of the Pyrenees, forming the heart of South-West France. Cave divers from all over the world return to dive here year after year. With over 20,000 known caves, France is one of the premier cave diving areas in the world. One of the most interesting regions lies in the Southwest, around the rivers of Lot and Dordogne. Here you find a multitude of long and deep caves with mostly crystal clear and relatively warm water, offering superb diving conditions. The water temperature averages 14º C/57º F and the visibility normally varies between 5-30 m/15-100 ft.

Finally!!! We can go to the Lot again. The COVID conditions have thrown a spanner in the works. But because we are all now vaccinated, we can finally leave. This time, for a week of training and then a week of diving holiday with my wife Caroline Massie. Two students (Jo Croimans and Bram Van Gorp) are with me for the training. The next few days, they will be busy with skills and dry teaching. Theory has already been given in Belgium so that we can get the most out of our dives. 

Why the Lot?

The area in France is popular because most European divers take cave classes there so they don’t have to travel to Mexico or Florida. One of the most famous caves around here is Ressel. Ressel is located in the village of Marcilhac-sur-Célé, in the heart of the Lot. Most pictures you can see online show huge, dramatic  blocks of white rock, flat structures, and the shafts of this cave. The facilities are pleasant, we have a large parking area for our cars, and finally there is also a conveniently located building with a toilet. From the car park we have only to walk about 100 m/330 ft to get to the entry point on the River Celé where we can put all our equipment needed for our dive.

Ressel History

The Ressel was first dived in 1968, by two divers of the speleo club Auvergnat. Martin and Debras reached 150 m/492 ft. It was only in 1973 that the line was extended to 300 m/984 ft, with a maximum depth of 30 m/100 ft. In 1975, Fantoli and Touloumdoian reached Pit 4 and went to a depth of 45 m/147 ft. Further exploration continued over the years, especially by Jochem Hasemayer in the early 1980s, where at 1100 m/3609 ft into the system he planted his knife in the rock to which he attached his line. This knife is still there.

On August 12, 1990, Olivier Isler was the first to cross Sump 1. The total dive time back and forth was 10 h 35 min. End of Siphon 1 is at Lac Isler, and from there on you can continue to the next siphons. Ressel consists of 5 sumps, of which siphon 1 is the longest (1850 m/6070 ft) and the deepest (83 m/272 ft). From Pit 4 onwards, the deep section begins, which can only be done with trimix mixtures. In the following years, the further sumps were explored by gentlemen like Rick Stanton, Martin Farr, and Jason Mallison. In 1999, the end of Sump 5 was reached. The total length on the main line is 4415 m/14,485 ft.

Spectacular Views In The First Section

To be honest, the visibility is spectacular all around. More than 10 m/33 ft visibility, which was near zero before the start in the Celé River—quite a change. As soon as we got to the entrance, the water cleared like snow in the sun. The first thought that ever crossed my mind was: How on earth did they find this cave? How, with the visibility of the river, did anyone see a hole that is 6 m/20 ft below the surface on one side—which is frankly not that big. Enquiries with the locals revealed that when the cave is full of water, you can even see a geyser in the river! Another impressive detail. 

There is a rope that runs from the point where you get all the way into the cave, and it continues to the main line; you don’t need a primary reel here—it’s really easy to find the entrance, at 6 m/20 ft deep. Then there is a huge tunnel with white giant boulders, which is impressive.

The first dives were only up to the T (180 m/591 ft penetration), where the obligatory skills were practiced, so that later one can widen the comfort zone. This is also a very beautiful part, especially because of the large blocks that lie here. There are even two exceptional phenomena visible; these are two blocks consisting of white limestone, with a large black spot in it. You won’t find these black spots anywhere else. It is wonderful to be able to admire nature like this.

My wife, the students, and I got in, and on the first dive, with a sidemount set consisting of 2×80 cf (dual 11 ltr) tanks, we did the first T, taking the left corridor. On the next T, we continued toward the shaft to a maximum depth of 30 m/98 ft to take a look. It is so impressive! We felt like we were going to the abyss, and actually we were, to the abyss below ground and underwater. But now they were even more curious about the famous Pit 4 of the Ressel.

To be able to do this dive, we had to bring the right amount of gases. The first dive was with Jo Croimans, my student; he had his sidemount configuration with an extra 7 ltr along, I dived with my Divesoft Liberty SM rebreather. There we went, all prepared. The way there is about a 28 minute dive. On the way, I showed Jo the shunt that goes to the deeper part of the first loop. Enjoying the ride, we continued until we reached the point of the shaft. 

Here I asked Jo if everything was Okay, he indicated that it was, and we descended to a depth of about 40 m/131 ft. I could see in Jo’s eyes that he was enjoying himself. But we didn’t have much time to enjoy ourselves, because we had to go back again. If you have deco, you can do it all on the way back on a nitrox 50 (NX50). For the advanced divers, you can take your oxygen at 6 m/20 ft and finish any decompression on O2.

It’s actually a great dive, and the cave allows for a variety of dives, just by choosing different depths in the tunnels, to have different perspectives.

Once we got to the top, Jo couldn’t stop exclaiming about the amazing beauty of this cave, and especially Pit 4. This made Caroline want to go and have a look too. This dive was done a few days later, when both gentlemen had gone home. This time we did the dive by scooter, a big difference. In 13 minutes we were at the shaft, and again I saw a happy face. How nice it is as an instructor to be able to pass on your passion. This is what we do it for. Ressel is one of the most beautiful caves in Europe. It remains an easy, accessible system.

The Ressel is and will always remain a special cave. Last year, I did the deep loop (1160 m/3806 ft long, 73 m/240 ft depth) here with two friends. And I still enjoy it when I talk about it. We still have to come back to do the rest of S1.

Additional Resources:

X-Ray: Pushing the Ressel—A Cave Diving Expedition in Lot, France by Erik Wouters (2013)

YouTube: Cave diving in France: Emergence du Ressel (2016)

Facebook: Here is a cave exploration project also going on nearby in Lot, France https://m.facebook.com/thehiddenriverproject. Find their map: here. 

Kurt Storms is a member of the Belgium military, and is an underwater cave explorer and active technical/cave/rebreather diving instructor for IANTD. He started his diving career in Egypt when he was on vacation, and the passion never ended. Kurt is also founder and CEO of Descent Technical Diving.  He’s diving on several CCRs such as AP, SF2, Divesoft Liberty SM.

Kurt is also one of the pushdivers that is documenting a new slate mine in Belgium (Laplet). This project was news on Belgium Nationale TV. Most of his dives are mine and cave dives.  In his own personal diving, Kurt’s true passions are deep extended-range cave dives. His wife (Caroline) is also a passionate cave diver. In his free time he explores Belgium’s slatemines. When he is not exploring, he takes his camera with him, to document the dives.

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