Jill Heinerth can proudly claim the title as the the world’s top underwater cave explorer. She has dived in places no other people have—including under deep Antarctic icebergs and through incredible underwater wrecks—and helped designed the first ever 3D map of an underwater cave. She’s also consulted for Hollywood and has produced a number of documentaries and books.
We talked to Jill about the dangers and rewards of extreme cave diving and why she keeps going back for more.

The Clymb: How did you get started in diving?
Jill Heinerth: I wanted to dive from my early childhood, but growing up in Canada, there were few opportunities that my family was aware of. I finally took a certification class during university and completed my open water diver certification in Tobermory Canada at Fathom Five National Marine Park.
The Clymb: And how did things move from “regular” diving to the extreme diving you do now?
JH: Almost immediately I took the bull by the horns and moved rapidly through other diving classes and continuing education. I was driving up to Tobermory most weekends and within a couple of years began instructing scuba at the entry level. I had such a passion for diving that I soon sold my advertising business in Toronto and moved to the Cayman Islands to dive full time. In the back of my head I knew I could find a way to combine both my passion for diving and my creative talents. I got hooked on cave diving and moved to Florida to live in the most popular region for cave diving in the world. It was in Florida that I began working in film and television projects associated with technical and cave diving.
The Clymb: You are an expert in one of the most dangerous sports in the world. Is that danger part of the excitement?
JH: Most people assume that I must be an adrenaline junky. I really don’t think the survivors in my sport fit that description. I am actually very risk averse. For me, cave diving and exploration are a great puzzle. I love it when somebody asks me to do something that has never been done before or go someplace that has never been explored. It’s not about the adrenaline, but more about putting the pieces and the team together to make it happen safely.

The Clymb: Can you talk about a trip or circumstance when you’ve felt you were in danger?
JH: I’ve had numerous close calls in exploration. I was pinned down by ripping current inside an iceberg cave in Antarctica. I’ve been trapped on the wrong side of a cave diver that was wedged tight in a body hugging restriction (the diver became the cork in the bottle that contained my life). I’ve been tossed like a rag doll in sixty foot seas and faced the business end of a rifle in a remote desert near the Libyan border. But perhaps my worst scare was fighting off a burglar with an Xacto knife in my home. In all those cases, I learned that you have to stuff the emotions back into some recess in your brain and maintain rational, pragmatic thought. You have to be able to take a deep breath and say, “emotions…you won’t serve me well right now,” and then get to the business of survival. You might not know how everything will work out, but you can keep taking baby steps towards survival. Just do the next best thing.
The Clymb: Can you tell us what is like to dive under giant Antarctic icebergs? Is the experience very different to diving anywhere else?
JH: My National Geographic Project to Antarctica in 2000, allowed me to make the first cave dives inside icebergs. It was an experience of a lifetime but perhaps one of the most dangerous things I have done. We traveled 12 days from New Zealand across the Southern Ocean on some of the stormiest seas on the planet. Nobody had ever dared to dive inside iceberg caves before, so we were re-writing the rules of engagement almost every day. On the final day of our project, after narrowly escaping a ridiculous current that pinned us down inside a tunnel in the iceberg, the iceberg we had just exited calved and exploded. A huge square mile of ice was pulverized into slush in mere minutes of destruction. We had only just gotten out of the water.
There was nothing like Antarctica…it was like traveling to another planet. I would return in a heartbeat.

The Clymb: What goes into extreme diving?
JH: Extreme diving takes endless training, lots of redundant equipment, and a cool head.
The Clymb: How is it different from the fun sport that so many people associate diving with?
JH: Technical and exploration diving takes people beyond the realm of recreation. In recreational diving, you can always just abort a dive and swim straight up. In technical diving we are often in overhead environments like caves and wrecks and under an obligation to decompress our bodies before surfacing. If we swam straight up, we could get decompression illness or die. In some cases, the decompression penalty can be extreme. My longest dive mission was over 22 hours.
The Clymb: Is it just about environments or is it also about discovery/learning/etc.?
JH: For me it satisfies a yearning curiosity—about our planet and undiscovered realms and also the depths of the human spirit…the ability to face challenges and embrace discomfort, to explore something that is meaningful to humankind. I often work with scientists on important projects looking at issues such as climate change or evolution or survival of uniquely adapted animal species.

The Clymb: Do you use any specialized equipment?
JH: One of my special areas of focus is the use of rebreathers. These devices recirculate your exhaled breath rather then dumping it in the form of bubbles. The gas is sent through a breathing loop to a scrubber that removes carbon dioxide from the mix and adds minute amounts of oxygen that have been metabolized by the diver. It is the same technology that is used for making spacewalks. We also use underwater scooters called “diver propulsion vehicles (DPVs)” as well as highly technical cameras, mapping devices, and other scientific sampling gear that can tolerate the underwater environment.
The Clymb: You’ve earned some very impressive accolades, including being inducted to the Women Diver’s Hall of Fame and receiving the Wyland ICON Award. Can you tell us a bit about these and other prizes/mentions you’ve won?
JH: I was inducted into the Women Divers Hall of Fame in 2000. I’m really proud of the organization that focuses on offering scholarships and training grants to young divers looking to find their way in the underwater world. I am most proud of receiving the first Medal for Exploration from The Royal Canadian Geographical Society. The medal recognizes lifetime contributions to exploration and I think it might have been the first time my parents really understood that what I was doing with my life had real merit!

The Clymb: Of all the dives you’ve done, what would you consider the best/most exciting one you’ve ever done? What made it so special?
JH: That is a really tough question…. Every dive has special memories. I think perhaps the most life changing project for me was the U.S. Deep Caving Team Wakulla Project. We made the first accurate 3D map of a cave system. The project was very deep and required some revolutionary thought. The team comprised of 150 volunteers who did everything from build technology to offer safety diving support. I had the opportunity to complete some diving goals that had never been achieved by a woman…and perhaps less than a handful of men. But what was far more important was the new understanding that I had with my water supply. We not only mapped the cave in three dimensions, but we linked it to the surface topography accurately. You could literally walk over the surface of the earth and understand what was below your feet…a major drinking water supply conduit for the State of Florida.
After that, I began to focus all my attention on projects that helped people better understand how what they do on the surface of the land would eventually be returned to them to drink. I have a unique opportunity to spread this “water literacy” as I call it and use my adventures to help people understand where their water comes from, how they might be polluting it, and how they can protect it for future generations.
The Clymb: Can you tell us a bit about the SEDNA Epic Expedition, its goals and how you got involved with it?
JH: The Sedna Expedition began with a goal to create outreach opportunities that helped people understand the issues of global climate change and how they were rapidly changing the Canadian North faster than almost anywhere else on the planet. We also wanted to create outreach opportunities that helped the indigenous communities of the north to better connect with their water resources. In 2014, we held a proof of concept expedition with an ultimate goal to snorkel the Northwest Passage as a relay of all women swimmers.
We traveled up the coast of Labrador and cut across the Davis Strait to Greenland and then on to Iceland. During the project we developed the safety protocols and techniques that would be needed to traverse the Northwest Passage in the future. I was the official underwater photographer on the project and was also brought along because of my cold water and expeditionary experience. I helped train many of the women in aspects of dive technology as well as expedition management and safety.