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Risking It All for Science

While some people might die doing science, a lot of people die cave diving: each year an average of 20 worldwide. The U.S. National Speleological Society defines a successful cave dive as "one you return from." "Extreme Cave Diving," the program I produced for NOVA, is really about the blue holes of the Bahamas. It's about cutting-edge science that gives us important data about our climate and reveals a lot about the Eden of now-extinct animals that once lived on the islands of the Bahamas. But blue holes are immense, flooded caves, and the only way to explore them is through the dangerous sport of cave diving.

ByJames BarratNova

cave divers Kenny Broad and Brian Kaku

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Expedition leader Kenny Broad (in the foreground), an anthropologist and expert diver, and Brian Kakuk, diving safety officer for the Caribbean Marine Research Center, prepare to delve into a blue hole.
© Jill Heinerth/National Geographic Television

In our 21-day expedition, and the resulting film, diving and the threat of dying sometimes overshadowed the science.

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Dying to Dive

Onboard we had some of the world's best divers. Dive leader Brian Kakuk is probably the planet's premier science and cave diver. Jill Heinerth is an internationally sought-after technical diving instructor. Wes Skiles, our director of photography, is arguably Florida's greatest cave explorer, living or dead. All our divers have been feature-film dive doubles or consultants.

Yet each knew several other, equally expert divers whose dead bodies they had recovered from caves. Including the expedition leader, anthropologist Kenny Broad, the dive team has recovered the bodies of more than 100 cave divers. To imagine recovering just one, think of a flooded, crumbling 10-story building at night. There's a dead body in the basement. You have to find it and drag it to the roof. Could you? What if it was a friend? Wes Skiles recovered the body of his best friend from a cave. He also recovered three brothers who realized they were hopelessly lost and out of air. Wes found them holding hands.

scuba man at water surface
To explore the dangerous realm of blue holes, the divers sometimes needed rebreather technology similar to that which astronauts use on space missions.
© Wes Skiles/National Geographic Television

Is diving really that dangerous? No, but diving in caves is. More people have died cave diving than climbing Mount Everest. Cave divers say of their sport, "There are no injuries, just fatalities." I've filmed in three war zones, but I think the chances of someone dying were higher in blue holes than in Iraq, Afghanistan, and Zaire. In the war zones, you hold onto the not-unreasonable hope that you can keep crew members alive by being extra careful.

Things can go wrong no matter how thoroughly you prepare.

I didn't think I could do anything about the dangers of the blue holes, except drain them—which is a ridiculous notion, and a crime, because damaging blue holes would be like burning a library.

Blue holes

At their deepest level, blue holes are anoxic, and this lack of oxygen helps to preserve whatever falls in. Our team was able to recover two skulls belonging to ancient humans, the fossils of vertebrates that are now extinct in the Bahamas, and fossils of birds that aren't just extinct but have never before been described by science. Living within the blue holes are at least one new order of multi-cellular creatures, descended from animals that evolved millions of years ago, as well as single-celled organisms virtually indistinguishable from the first life-forms on Earth. Parts of blue holes are like our planet's first seas, from a time four billion years ago when the Earth had no oxygen. NASA was interested in the expedition because the extreme life-forms found in blue holes are similar to what they hope to find on other planets.

scuba diver with skull
The deep, oxygen-free zone of one of the caves preserved an 800-year-old human skull, shedding light on the Lucayan people who inhabited the Bahamas long before Columbus visited.
© Jill Heinerth/National Geographic Television

In the geological sciences, blue holes hold just as many wonders. When cut open, stalagmites from blue holes display layers like the rings in a tree. Analysis of their composition reveals a year-by-year diary of the Bahamas' climate for the last 200,000-300,000 years, including rainfall, the chemicals in the rain and air, even the temperature. They don't just record past periods of extreme climate change, but also tell us how fast that change can grip the planet.

My greatest challenge in making "Extreme Cave Diving" was learning enough about the different sciences related to blue holes to interview the scientists who joined the expedition: marine biologist Tom Iliffe, ornithologist David Steadman, molecular biologist Jenn Macalady, cave scientist Nancy Albury, geochemist Peter Swart, and others. The second greatest challenge, with which I had a lot of help, was writing and editing for months to squeeze an often unpredictable expedition with untidy results into a neat package of one-hour television.

Tom Iliffe holding vial with intertebrate in it
Biologist Tom Iliffe studies the unique invertebrates found in blue holes. Because the ecosystem is isolated, animals have evolved here that live nowhere else on Earth.
© Jill Heinerth/National Geographic Television

Everything but the sweat

We traveled and lived on the 66-foot S.S. Tiburon, an expedition ship that had just enough room for our crew of some 14 people and about four tons of gear, including dive gear, cameras and related paraphernalia, computers, printers, junk novels, and about 50 tanks for various mixes of air. We lacked for nothing in amenities on the boat, though our close quarters meant that a virus remained in constant circulation among the team. Most importantly, the AC worked—July in the Bahamas is the hottest and most humid month of the year.

We shot at seven blue holes in about 21 days. On a typical day, we'd rise with the sun, offload gear from the ship into vans, then go to the hole and put together a rough base camp. We'd film the dive preparations and jump-ins, and then we wouldn't see the dive and underwater film team until they emerged carrying their scientific finds, usually two or three hours later. So, at some part of each blisteringly hot day, everyone would vanish into the deep except for a scientist or two, my topside cameraman, the gifted and tireless Gordy Waterman, ace soundman Dave Strayer, and me.

We'd use this time to shoot interviews with the film's characters who weren't diving, or laboratory scenes with our scientists examining blue hole finds. At night we'd review tapes, log their contents, back up media, and have a production meeting to discuss what was working and what wasn't. The underwater crew had tanks to fill and gear to prep and repair. We'd hit our bunks around midnight, smelly and exhausted. To imagine what our lives were like, think of the glamorous, gin-soaked Bahamas of Casino Royale. Now take away everything but the sweat.

James Barrat in water with cameraman
Producer James Barrat (left) got accustomed to conducting interviews while standing shoulder deep in the waters of a blue hole.
© Jill Heinerth/National Geographic Television


I kept track of the divers' morale and health, both of which had ups and downs, and I sometimes worried about them. They are an exceptionally proficient group—masters of knots, knives, seamanship, and, of course, diving. Otherwise, they wouldn't have been much use to a film or a scientific expedition, and, frankly, probably would've died long ago.

However, there's a term our divers used called "task-loading," which means unconsciously adding tasks to the things you have to do, or being conscious that you're over-burdened and not speaking up. Task-loading kills people. The dive team was task-loaded to the gills. In addition to the variables of technical diving and collecting samples, they had to contend with the problems of lighting and filming underwater. Add to that the ordinary hazards of cave diving—cave-ins, silt-outs, faulty gear, decompression sickness, nitrogen narcosis, oxygen toxicity, running out of air, and, of course, simple, everyday drowning. Take all that and put it on a tight schedule. Oh, and whenever you're above water you're being filmed, and the producer expects you to be engaging 24/7.

diver hauling container
Only seasoned cave divers like Brian Kakuk could safely handle the complexities of recovering scientific samples from the labyrinthine depths.
© Jill Heinerth/National Geographic Television

But we came back with no injuries, largely because we were wary, and we had planned to be wary. While pushed, no one dived whose ability or safety was compromised, as far as I know. Sick people stayed in bed. Besides being our chief science diver, Brian Kakuk was also the diver in charge of safety, and he has an uncanny sixth sense about other divers. So we had a good safety structure. Other than a couple of rebreather malfunctions and a small cave-in, we had no dive-related safety incidents.

You may endanger everyone on a dive by having one unlucky moment.

Things can go wrong, of course, no matter how thoroughly you prepare. For example, it's nearly impossible to predict avalanches of loose rock, and big cave-ins. In the film, Kenny Broad says, "We're swimming over boulders the size of houses, and you know they came from the ceiling." I've no doubt that luck played a part in our expedition, and that teams with even greater attention to safety than ours have lost members.

In the end, I took away a great appreciation of the divers' self-reliance. I'm a PADI Rescue Diver—which on this shoot was a qualification about as useful as being a good singer—and I've always had drilled into me that you never dive alone. You dive with a buddy. In cave diving, however, you may head into a cave with several buddies, but you're always diving alone. That's not existential hyperbole—if something goes wrong in a cave, your buddy probably can't help you. You train to self-rescue. You're just too far from safety to think about survival any other way. In fact, you may endanger everyone on a dive by having one unlucky moment. Suppose, for example, that you're the last person to squeeze through a tight passage and you get hopelessly stuck. One second you're a valued member of a cave-diving team. In the next, you're the cork in the bottle containing the lives of your friends.

Major funding for NOVA is provided by the David H. Koch Fund for Science, the NOVA Science Trust, the Corporation for Public Broadcasting, and PBS viewers.