Caught in an Underwater Avalanche

Kenny Broad, an environmental anthropologist and National Geographic Expeditions Council grantee, says the first rule in cave diving is to always run a continuous guideline.

Broad and his team have done hundreds of exploratory dives in blue holes, submerged caves that can have zero visibility—and where the guideline can become the only means to find their way back out. “A lot of great divers end up getting lost and actually never come out of underwater caves," he says. "What looks like crystal-clear water … You may turn around and you can't even see your hand in front of you, not only because you may go into complete darkness, but because you might have stirred up the real fine silt on the bottom. Your bubbles may have hit the roof and just knocked off sediment.”

Zero visibility is only one of the challenges. Broad says it's all about multitasking. “One of the big problems is getting distracted. That’s why you've not only got to keep track of where your guideline is, you've got to make sure you're saying, ‘Okay, how much of my diving gas am I using? Am I switching back and forth between tanks? Am I navigating properly? Am I not damaging the cave?’ It's this trade-off between sensory overload of aesthetics and keeping your life support system going.” Making sure you have a hand on the line throughout the dive gives a whole new meaning to “hanging by a thread.”

You can read more about the Blue Holes Project here

Find out more about Kenny’s work here

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PRODUCER/EDITOR: Carolyn Barnwell
SERIES PRODUCER: Jennifer Shoemaker