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"I’m a qualified cave diver – here’s why the Thai rescue was so terrifying"

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Kera Rolsen
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A qualified cave diver in a cave

Three of her friends have died cave diving in the last decade. Here, cave diver Kera Rolsen explains exactly why it’s so dangerous

Picture yourself underground, deprived of sound, sight, and surrounded by frigid water – desperately trying to fit through a hole in rock so small you must push your air tank in front of you. In the summer of 2002, I found myself in that scenario, attempting to navigate what is called a “no mount restriction”. I was a fully trained and qualified cave diver and I was still nervous. Heart pounding, breathing hard, and extremely aware of the ten metres of water and rock that stood between me and the surface. I successfully completed that dive as a fit, healthy, 20-year-old cave diver, filled with the sense of invincibility only a young adult can possess.

To understand what the recent (and fortunately) successful rescue of 12 boys stuck in a Thai cave was like, imagine the scenario above but this time you are a young man, starving and weak with fatigue. You’ve been separated from the surface and your family for two weeks. Your only way out is through the unknown murky depths that have sequestered you. You have no previous training but now must cave dive to save your own life.

But what is cave diving? At its heart, cave diving is exactly what it sounds like: scuba diving in a submerged tunnel. However, there are some very important differences between open water diving and cave diving.

I’m a qualified cave diver – here’s why the Thai rescue was so terrifying 1

Kera cave diving (Credit: Harry Averill)

Cave diving differs from open water diving in three main ways: environment, training, and the gear. The most obvious is the environment. Open water divers are not certified to enter any overhead environments, which could be a wreck, cavern, or cave. The line between cave and open water is drawn where sunlight ends; if you can no longer see sunlight, you’ve entered the cave. 

Diving through a labyrinthian underwater cave  presents unique challenges. In an emergency, an open water diver can choose a direct ascent to reach the surface, even risking decompression sickness in an extreme emergency. However, this is not an option for a cave diver. In the event of a medical emergency or catastrophic gear failure, the only way out is the way in, the long trek back the way you came. That route can be fraught with narrow passage ways and silty floors that wreak havoc on visibility.

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Thai soldiers working on a rescue effort outside the Tham Luang cave, where the boys were trapped (Credit: Getty) 

These challenges bring us to the second difference: training. The unique environment requires divers to learn a myriad of specialised skills like how to find the guide line in near-zero visibility, crucial to a safe exit. They also must learn new kicking skills and practice precise buoyance control to keep from disturbing a silty floor that if disturbed could leave you with almost zero visibility.

Cave divers also must learn “difference gas management techniques”. In open water, when you hit your decompression limits, you start an ascent. In cave diving, one carefully manages their gas “on thirds”, leaving when you’ve used one third of your air supply. This ensures that you have twice the necessary gas to get back out in case of an emergency such as you or your dive buddy suffering a gear failure that requires you to share air.

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Scuba tanks used for the Thai cave rescue (Credit: Getty)

Which leads me to the third difference between open water and cave diving: gear. Cave divers carry everything an open water diver carries (minus the snorkel which could create a safety hazard by becoming entangled in lines or rocky outcroppings). Their wetsuits are thicker for the colder water, fins are stiffer for fighting currents, and they will usually carry two tanks. In addition to the standard open water gear, they will also carry three lights and a spare reel of line. Finally, they rig up their gear in such a manner that it stops them from having “the dangles”: free floating gear that can get snagged or entangled.

Let’s get back to the topic everyone’s talking about: the Thailand cave rescue, which was successfully completed earlier today. 

What rescuers probably didn’t tell the boys and their coach is that since cave diving became a sport in the 1950s, over 300 people have died in caves. Sadly, three of the divers in that stark statistic are friends of mine that have passed during the last decade. When my dive buddy from a trip in 2001 died four years ago, it caused me to rethink my participation in the sport and drastically reduce the number of dives I do.

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(Credit: Harry Averill)

Given the hazards of the environment, the training, and gear required it’s easy to see how 300 people have perished. Now on top of all that, envision yourself in the Thai cave environment: starving, weak from exhaustion and scared. These are not the ideal cave diving students: they are the very opposite of ideal. 

The decision to train the Thai boys was truly life and death. The rescue divers faced the same dangers any other cave diver faces with one addition: they had a dive “buddy” who could not help. The boys lacked the knowledge or experience desired in a typical dive buddy whose gear should provide redundancy for yours. 

I have only the utmost respect for the rescue that occurred. Given the additional dangers imposed by the scenario, these rescue divers embody selfless heroism.

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