Cave diving is one of the most dangerous sports on Earth, and for Jill Heinerth, it's her job.

The Canadian explorer, writer, and filmmaker has spent more than 30 years exploring underwater caves, and has now written about her career in a book: Into the Planet, my life as a cave diver.

"It's like swimming in the veins of Mother Earth for me. I'm in the sustenance of the planet," said Heinerth.

She points out the only unexplored places on the planet are underground, and underwater.

"The opportunity to go to a place that nobody has ever been before, and bring back images and video from those places, to share, is incredible," said Heinerth.

For more about Heinerth, how dangerous her work is, and how she avoids risk, watch the interview.