A scuba diver measures the length of Sac Aktun underwater cave system in Tulum, Mexico.Herbert Mayrl / Courtesy Gran Acuifero Maya Project

“Rescues are actually pretty rare.”

What Robert Laird, the co-founder of International Underwater Cave Rescue and Recovery, means is this: When cave divers get in serious trouble, they usually die. There is no one to rescue, just a body to recover.

In Thailand, an extraordinary rescue effort played out this week for 12 boys and their soccer coach, who managed to find high ground when floodwater trapped them in a cave. To get out, these boys had to dive through those same floodwaters.

It’s a perilous journey even for experienced divers, as underscored by the death of a Thai Navy SEAL in the cave last week. Cave diving is a different beast from diving in the open waters. The water can be so muddy that divers have to feel their way out. The passage can be so narrow that you have to take off your air tank. And you cannot simply swim up to safety. By Tuesday morning, divers had miraculously guided all 12 of the boys and their coach out of the cave under these conditions.

I spoke to Laird on Monday about underwater rescues and the unique dangers (as well as the rewards) of cave diving. Our conversation had been condensed and edited for clarity.


Sarah Zhang: What makes cave diving so dangerous?

Robert Laird: The one thing that kills divers more than anything else is panic. It can start with a small thing, like suddenly you see bubbles coming off a hose. That seems so trivial and minor but that can immediately put doubt in a mind because you’re in a cave. There’s no escape. There’s no quick way up. It tends to cascade.

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When you’re panicked, there’s absolutely no logic. There’s no reasoning. There’s no logical method of thinking. I’ve seen panicked people underwater, and they do not behave normally. You can even point the way out to them and they look at you like you’re crazy, and they’ve convinced themselves another way is the correct way. They may swim into the cave, rather out of the cave to safety.

Zhang: What do you have to do differently when diving in a cave?

Laird: I would say the most important thing is being able to maintain absolute neutral buoyancy, so you don’t drift up into the cave ceiling and you don’t drift down into a very, very silty bottom. If you hit the silt, you can end up in a “silt out,” which means that silt fills the room that you’re in. You put your head underwater and you look and you can’t see anything. You can put your light against your mask and you can see your light, and that’s about it.

Typically in a large cave with known visibility that’s fairly good, the chances of a complete silt out that you can’t wait out are fairly small. The area that’s really bad is sump diving, which is where you have a dry cave that has tunnels that sometimes go underwater and sometimes come up and through air again.

Zhang: Like the cave in Thailand?

Laird: Which is much like the Thailand case. Those sumps are typically very, very silty. You have to have some specialized experience to traverse these silts successfully—with the idea you’re not going to be able to see, you’re not going to be able to communicate.

Zhang: What mistakes can experienced open-water divers make when they start diving in caves?

Laird: Experienced open-water divers, unfortunately, think that they are qualified to dive into caves, but they’re not. There have been lots of extremely experienced open-water divers that have died in caves. The main one is the rule of thirds, which is reserving the amount of air that you have left, so that you always have two-thirds of your tank available at your furthest penetration. There are lots of examples of open-water divers that dive into a cave and they dive into the halfway point of their air. Cave divers look at the situation and go, “They’re already dead and they don’t know because they’re probably not going to make it out.”

That’s because you may not be able to go out with exactly the same amount of air you went in with. All you need is 30 seconds of no air and you essentially can’t go up to the surface. Chances are you’re not going to make it.

Rescue teams pumping water out of the flooded Thai cave (Royal Thai Navy / AP)

Zhang: Have you ever had a close call?

Laird: I was diving with a buddy and we were probably a mile back in the cave, and his regulator [which delivers air to the diver] started free-flowing, which basically means he was going to run out of air very quickly. This was a multi-tank dive, where we had staged bottles over a period of time to make sure we had enough air to come out safely. We were just way, way back in the cave. Having two people come out on one set of tanks and going through the multiple stages [is] extremely complex. You just can’t make any mistake.

There was another time when I was doing an extremely deep dive. I picked up the wrong bottle of air. I was starting to breathe it and I was going deeper and deeper with this bottle, and I suddenly realized it was the wrong bottle. If I continued without realizing, I probably would have had a seizure and drowned. When you go deeper you have to use trimix, which is a combination of oxygen, nitrogen, and helium. If you have the wrong mixture for breathing deeply then you can get oxygen toxicity [too much oxygen]. That’s usually fatal. Even nitrogen narcosis, if there’s too much nitrogen in the mix, and you would get the equivalent of being drunk and you can make poor decisions and run the risk of drowning.

Zhang: Can you tell me about some rescues your organization, IUCRR, has worked on?

Laird: One the earliest ones that was remarkable was when they went to a cave expecting it to be a recovery. The cave was not known to have any airspaces. They found the person waiting on the beach, had been there two or three days by themselves. They were convinced they were dead. So when they saw the lights of the cave divers through the water, they thought the angels were coming to get them. They were brought out safely.

We’ve had a few other incidents where a diver ran out of air, but was able to find an air bell. You can breath off one of those for, if you’re lucky, 15 to 20 minutes without saturating it with carbon dioxide and passing out. The rescue-recovery diver was able to get in the water very quickly and find them and saw they were in this air bell and was able go up there and talk to them and calm them down and basically give them their second regulator and swim them out.

Most of the recoveries are pretty gruesome to talk about.

Zhang: I can imagine, especially if the body has been in the water for a while.

Laird: Exactly. Most people don’t know the bodies expand. Sometimes they get very difficult to remove, become too buoyant.

There’s a lot of stuff the public doesn’t really realize. Since law enforcement considers these to be crime scenes, you have to follow law-enforcement protocol. If you don’t have a camera, you have to try to remember the way the scene was to describe it later. You’re not supposed to touch their equipment unless it’s required for removing the body. You have to make sure the public is separated from the diving operations, so they don’t interfere. You have to plan for when the body comes up so the family members don’t witness that, because it’s usually very upsetting.

Recovery sounds like, “You swim in and you get a body and you swim out.” It’s never that simple. It’s usually very complex, very arduous process, and it’s exhausting to do recovery. Not only is the physical task load enormous, but the mental and psychological tasks of dealing with a dead body—that most people probably couldn’t do. All those things add up. A lot of times you have to do multiple dives to be able to retrieve the body because of the complexity and the difficulty.

Zhang: We’ve been talking about the dangers of cave diving. So why do it all? What’s the appeal for you?

Laird: It’s a technical challenge. Usually, people that get into cave diving are already very capable open-water scuba divers and they’re looking for something more challenging. My particular reason is I want to see stuff. I take cameras along everywhere I go and I take pictures of things that I do.

And some people like to explore. The easy stuff, the low hanging fruit’s probably been done. So that means more and more technical challenges in exploring these caves. There’s plenty of places where you can go into a cave nobody has ever been into before. You think, “Well, more people have been to the moon than have been in this cave.” There’s still plenty of cave to explore. There’s enough caves in just the Yucatán Peninsula of Mexico for all the cave divers in the world.