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FeedSource: [ArsTechnica]

Time: 2018-07-22 13:50:58 UTC

Original URL: https://arstechnica.com/features/2018/07/risky-thailand-cave-rescue-relied-on-talent-luck-and-on-sticking-to-the-rules/ [arstechnica.com] using UTF-8 encoding.

Title: Risky Thailand cave rescue relied on talent, luck—and on sticking to the rules

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Risky Thailand cave rescue relied on talent, luck—and on sticking to the rules

Arthur T Knackerbracket has found the following story [arstechnica.com]:

Last week, the world was riveted by the successful rescue of a youth soccer team as they and their coach were pulled out of a flooded cave in Thailand. The team had been stranded on a narrow rock shelf in the dark for two weeks, the way out blocked by turbid stormwater. The rescue involved far more than a few divers putting on gear and heading into the cave—it required a tremendous amount of technical skill and posed extreme danger.

But why, exactly, was it so dangerous? And what would it feel like to dive in those kinds of conditions?

But to answer the second question, I decided to open my logbook and go back to a dive from many years ago—well before I was diving professionally. As a few select passages below highlight, this was a dive where things almost went fatally wrong.

Cave diving has five rules [bestpub.com]. These sum up the hard-won wisdom of the cave-diving community, as conducted through the analysis of cave-diving accidents and fatalities. Though the exact wording of each will differ from instructor to instructor, the rules are:

Since these rules were introduced in the late 1970s (first as only three rules, later expanding to five), fatalities per number of dives have dropped among the cave-diving community. Today, the largest segment of fatalities in underwater caves comes not from certified cave divers but from divers not specifically trained by a professional cave instructor to be in that environment.

The first of these rules is therefore simple, and one that I broke badly: never dive beyond your certification level.

This rule alone would have made the rescue a challenge. The boys trapped in the Thai cave had no diving—and in some cases no swimming—experience when they had to dive into the waters blocking their passage to the surface of their dark prison. Their first experience underwater in a cave was probably terrifying, with very low visibility, buffeting from high rates of water flow, strange booming and rumbling sounds from their expelled breathing gas moving across the ceiling, and the glowing orbs of their rescuers' lights.

One of the major technical challenges in the Thai cave was to get the boys through a 15-inch-wide (about 38cm) restriction in the cave which exited the water on an incline. The rescue divers reportedly stationed themselves in front of and behind each boy during the underwater portion of the rescue, which is standard practice in an emergency situation. Unfortunately, due to the small size of the restriction, the divers had to remove their tanks and push them ahead of or drag them behind while also tending the victim and the victim’s scuba tank.

This would have been extremely claustrophobic for all involved (seriously—grab a tape measure, reel it out to 15 inches, and imagine squeezing yourself through an irregular hole about that wide at its widest point). For a while, all the boys would be able to see would be rock right in front of their faces while feeling rock scraping along their bodies on all sides. During their time in the restriction, the rescue divers would also lose some ability to check on the victim.

Another rule of cave diving is to use only one-third of your entire gas supply on the way into a cave—leaving another third to exit and the final third for handling emergencies. Unsurprisingly, this is called “The Rule of Thirds.” This approach also leaves enough gas to help a diver who has experienced an equipment failure breathe off a dive buddy’s gas tanks, making it back to the cave entrance even from the furthest point in the dive.

In Thailand, one of the first things needed after the soccer team was discovered was to deal with the logistics of supporting all of the dives required to effect a rescue. This would mean having support divers cache breathing gas tanks ahead of the main rescue divers so they would have enough breathing gas to make it to the boys’ perch in the cave and back out. Every time a dive was completed, the support divers would have to clear the used tanks and place new ones for the next set of dives, dragging tanks in and out of the cave repeatedly. Even these support dives were fraught with danger, as evidenced by the loss of one of the support divers [npr.org] who ran out of breathing gas on his way out of the cave after placing tanks for the main rescue divers.

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