Jill Heinerth is the world’s leading underwater cave diver, and her quest to understand what lies beneath the surface of our planet has taken her to some incredible places.

“I have cave-dived beneath golf courses, bowling alleys, homes,” she says. “My favourite was under the salad bar of a Sunny’s BBQ restaurant while a surface tracking team was walking between the tables yelling, ‘cave survey, coming through,’ and planting an orange flag in a salad bar potato salad.”

Heinerth’s dives have also taken her into lava tubes in underwater volcanoes, oases in the Sahara desert and flooded mine shafts. She has set records for the longest and deepest recorded cave dives, including for the longest dive inside an Antarctic iceberg. In 2016, she became the inaugural Explorer-in-Residence of The Royal Canadian Geographical Society, and she continues to push her own boundaries in pursuit of the thrill of discovery. 

“When I was a kid, people said the age of exploration was over,” the Mississauga, Ont. native recalls. “As a kid who wanted to explore and go to a place that ‘no man had been before,’ for me inner earth was left. We know more about space than we do about our oceans; we know even less about underwater cave environments and what lies within the earth.”

Cave diving is incredibly risky, and Heinerth says managing fear, especially in a crisis, has been a big part of her success over her decades-long career.

“I know that when something really horrible happens, the first thing I have to do is quiet my mind and tell myself that my emotions won’t serve me well right now,” she says. “The emotions only make me breathe fast and my heartbeat go faster, which means you use up your tank of gas faster.”

A big part of Heinerth’s mission as RCGS Explorer-in-Residence is leading discussions in schools and communities about Earth’s most precious and fragile resource. 

“Clean, fresh drinking water is a very finite resource,” she says. “As I swim through these environments, I hope that I can communicate to people that everything we do on the surface of the earth is going to be eventually returned to them to drink.”

This episode is produced and sound engineered by Robin Dumas, and hosted by David McGuffin (@mcguffindavid).