Cave Diving: One of the Most Dangerous Sports in the World?

A sport for explorers with nerves of steel.
Marcia Wendorf
A diver underwater.Extreme-Photographer/iStock

On Saturday, June 23, 2018, 12 members of a local Thai football team, who were between the ages of 11 and 16, and their 25-year-old assistant coach, entered the Tham Luang Nang Non cave for a day of exploration.

What should have been a fun day turned into a nightmare when early monsoon rains flooded the cave, which is located on the border between Thailand and Myanmar, cutting the boys off from the entrance. The group scrambled 2.5 miles (4 km) from the cave's entrance before they found refuge on a rock shelf that remained above the water.

At 7:00 p.m., the football team's head coach began receiving phone calls from worried parents, asking where their children were. Racing to the cave's entrance, the coach found the boys' bicycles still parked outside, and he alerted Thai authorities. On June 25, 2018, Thai Navy SEALS began a search of the cave, which was hampered by near-constant rainfall.

The world responds

Cave Diving: One of the Most Dangerous Sports in the World?
The international team of divers. Source: USAF/Wikimedia Commons

In what is an amazing coincidence, a British cave explorer named Vern Unsworth was exploring the Tham Luang Nang Non cave and lived nearby, and he suggested that the Thai government contact the British Cave Rescue Council (BCRC). On June 27, three highly specialized cave divers from BCRC arrived at the cave, followed on June 28 by a team from the 320th Special Tactics Squadron, 31st Rescue Squadron of the U.S. Air Force. The next day, divers from the Australian Federal Police Specialist Response Group arrived at the cave, followed by a Chinese team from the Beijing Peaceland Foundation.

While Thai authorities looked for another way into the cave, such as drilling from above, two of the BCRC divers, Richard Stanton and John Volanthen, along with Belgian diver Ben Eeymenants and French diver Maksym Polejaka began laying guidelines through the cave's murky water. Increased rainfall forced all the divers to retreat from the cave until July 2, 2018. When Stanton and Volanthen finally discovered the boys, they all were, incredibly, still alive, though they were very hungry.

Thai Navy SEALs, along with the BCRC divers and the Australian and Chinese diving teams, began transporting tanks of breathing gas into the cave system, while several Thai Navy SEALs and a Thai Army doctor tended to the boys. In all, an estimated 10,000 people took up residence at the cave's entrance, including the Thai military personnel, engineers, government officials, volunteers, news media, and the families of the boys.

Cave Diving: One of the Most Dangerous Sports in the World?
Rescuers pumping water. Source: USAF/Wikimedia Commons

To keep the rising water from drowning the boys, engineers were able to pump over 1 billion liters of water from the cave, but that didn't stop the oxygen level in the cave from dropping to a dangerous level.  It took highly experienced cave divers six hours, swimming against the current, to reach the boys, and it took them five hours, swimming along with the current, to exit the cave. The rescuers doubted that the boys could remain calm for that duration while wearing SCUBA gear and remaining underwater, especially as many of the boys did not know how to swim.

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Out of time

With a weather forecast of additional monsoon rains that would flood the cave until October and oxygen levels in the cave falling rapidly, rescuers decided to attempt a rescue on July 8, using 13 international cave divers and five Thai Navy SEALs. Four British divers, Stanton, Volanthen, Jason Mallinson, and Chris Jewell, along with two Australian divers, Craig Challen and Richard Harris, entered the cave, supported by 90 Thai and foreign divers who would perform medical checks on the boys at various points, and provide fresh air tanks.

Besides being a cave diver, Harris was also a physician, who would sedate the children, and because the sedatives lasted only around an hour, Harris trained the divers to re-inject the boys. 

Once they reached a staging area deep within the cave, hundreds of volunteers passed the children along zip lines, which had been installed by rock climbers. Each boy was wearing a full face mask and was attached to the guide rope and to a diver in front, who also carried the boys' oxygen tank. A second diver followed each boy, carrying a flashlight.

Once they reached a dry chamber near the mouth of the cave, the boys recovered from the anesthetic and walked out.

On July 8th, four boys were rescued, and the following day, four more were rescued. On the third day, the last four boys and their coach were rescued.

Last out of the cave were the three Thai Navy SEALs and the Army doctor who had stayed with the boys. However, once they reached the staging area, Chamber 3, water started flooding the cave and they, along with the 100 rescuers still inside, were forced to make a mad dash to the cave's entrance, emerging unscathed. The cave did claim two lives: former Thai Navy SEAL Saman Kunan, who was volunteering, died while placing air cylinders along the escape route, and a year after the rescue, Thai Navy SEAL Beirut Pakbara, died from a blood infection he had caught while in the cave.

The most dangerous sport

Cave diving is so dangerous because divers cannot swim vertically to the surface, but they must retrace their steps to the cave's entrance. To be successful, cave divers must undergo rigorous training, the first level of which includes entering the overhead environment of caves, guideline and line reel management, breathing gas planning, propulsion techniques, and communication techniques.

Cave Diving: One of the Most Dangerous Sports in the World?
Diver stringing guideline. Source: Ryan Cantey/Wikimedia Commons

The second level of training, apprentice cave training, includes the use of sidelines off of the main guideline, navigating multiple jumps, or gaps, in a guideline, and decompression techniques. Further training includes cave surveying and mapping techniques.

In 1979, Sheck Exley published the book, Basic Cave Diving: A Blueprint for Survival, which broke down the factors that contributed to cave diving accidents. The five factors Exley identified are:

    • Training - cave divers must not exceed their level of training, and academic training must be accompanied by a real-world experience.
    • Guideline Management - besides fixing a guideline from a point outside a cave, additional tie-offs within a cave must be made, and guidelines must not be allowed to fall into traps; line arrows, which are notched triangles, should be placed on guidelines to provide both visual and tactile reference to exits, orientation, and the locations of jumps.
    • Breathing gas management - divers must use the "rule of thirds," where one-third of breathing gas is used for ingress, one-third for egress, and one-third kept as an emergency reserve; use of secondary gas systems is also encouraged.
    • Depth management - because caves plunge deep within the ground, divers can accidentally exceed their expected depth, which can affect their breathing gas consumption, and increase the need for decompression. 
    • Illumination - a cave diver should carry at minimum three independent sources of light, with the first intended for use during the dive, and the other two considered backup lights; each light must have a burn time of at least the planned duration of the dive, but backup lights may be lower powered.
Cave Diving: One of the Most Dangerous Sports in the World?
A diver using side-mount cylinders. Source: Pete Nawrocky/Wikimedia Commons

Cave divers use different configurations of breathing gas tanks than open water divers, and they also breathe mixed gasses such as trimix, which is comprised of oxygen, helium, and nitrogen, and nitrox, which is comprised of nitrogen and oxygen.

Cave diving was pioneered during the 1930s in the UK when members of the Cave Diving Group (CDG) explored the flooded caves of Somerset. During World War II, underwater warfare was pioneered, and following the war, lots of surplus equipment became available. The 1960s brought the first use of the wetsuit, which provided both insulation and buoyancy, SCUBA air systems, fins, and helmet-mounted lights.

Cave Diving: One of the Most Dangerous Sports in the World?
Florida warning signs. Source: Greg Grimes/Wikimedia Commons

During the 1970s, cave diving caught on in the U.S., but with no official training, fatalities started mounting. This was especially true in the state of Florida, which came close to completely banning cave diving within its borders. Today, popular cave diving locations include Grand Bahama Island, and north-central Florida, which is home to the longest explored underwater cave systems in the U.S.: the Leon Sinks and Wakulla Springs.

A wild ride

For sheer excitement, nothing tops the cave diving exploits of the American engineer and cave diver Bill Stone. In 1998, Stone directed over 100 volunteers in exploring Wakulla Springs. Stone next worked with NASA to produce an advanced autonomous underwater vehicle (AUV), and he participated in a project for developing a vehicle capable of exploring the underground seas of Jupiter's moon Europa.

In December 1987 at Wakulla Springs, Florida, Stone used a Cis-Lunar MK1 model rebreather to stay underwater for over 24 hours, using only half of the system's capacity. In 2010, author James Tabor wrote Blind Descent: The Quest to Discover the Deepest Place on Earth. It describes Stone's explorations of the Mexican caves Huautla and Cheve, and Ukrainian Alexander Klimchouk's exploration of the Republic of Georgia's cave Krubera.

Cave divers continue to push the boundaries of what is possible as they survey and map the world's deepest places.