"Oh, gosh, I am not fearless. I am scared all the time!” protests explorer and cave diver Jill Heinerth. “It’s how I prepare to deal with scary situations and risk that has kept me alive. But I am still not fond of driving. All those people careening out of control on highways make me nervous.”

If you know her—or have been taught by her or watched any of her documentaries or read her stories in this magazine or, more recently, caught her on NPR’s Fresh Air, talking about her new book Into the Planet: My Life as a Cave Diver—you can hear Heinerth’s mellifluous voice behind the email.

That’s a principal joy of Into the Planet (Ecco; $26.99), a memoir about her transformation from a Toronto graphic designer with a yen for broader horizons to Explorer in Residence for the Royal Canadian Geographical Society. The book reads as though Heinerth is speaking directly to you, in her understated way, quietly and simply telling a story that is anything but.

WHY WAS NOW THE TIME TO TELL THIS TALE?
“I’ve been working on this for the better part of 10 years! It took me a while to find my voice. Writing about your life and choosing to reveal personal details is daunting. After a prominent literary agent reached out to me, I figured it was a sign to get to work finishing the book.”

WHAT WAS THE HARDEST STORY TO TELL?
“My editor became more of a psychologist, urging me to get personal and share details of relationships and emotions. That said, it was extremely difficult to write about my dead friends. When I recorded the audiobook, I kept breaking down, and could not even get through my own written words. Finding a way to honor my former creative partner Wes Skiles [a National Geographic photographer who died in a rebreather accident in 2010] in a way that balanced the tough background story was extremely challenging too. I really miss him and hate the way he died, but I want the world to know the contributions he made to diving safety and water advocacy."

MORE: Read Jill Heinerth's articles here.

YOU’VE SACRIFICED A GREAT DEAL TO REACH THESE HEIGHTS — DOES JILL HEINERTH HAVE REGRETS?
“I offer that all the good, bad and ugly experiences that we have in the end are positive; they build who we are today. There are times I wish I had spoken up more, but comfort in your own skin comes with experience and wisdom. If I had challenged the old guy who told me there was no place in commercial diving for women, I would have had a different life completely.”

WHAT BRINGS YOU THE MOST JOY?
“When I am speaking to a classroom full of kids and I reach one with a spark of inspiration. My most important role now is to pass on what I have learned, and be the woman I wish I had met when I was 10 years old. In diving, it’s the sublime stuff. Alone on the floe edge in the Canadian Arctic, preparing for a dive while a polar bear moves in, or just sitting in the cavern zone of a turquoise spring while the sunbeams penetrate the water—I am in my element.”

Buy *Into the Planet: My Life as a Cave Diver*