“You see these massive calving fronts breaking off icebergs… you hear it, you feel the vibrations… everything is just absolutely magical.”

In this episode of Explore, podcast host David McGuffin welcomes back legendary underwater explorer Jill Heinerth to talk about her powerful new documentary, The Berg, airing on CBC’s The Nature of Things and streaming on CBC Gem.

For years, Heinerth dreamed of following the full lifecycle of an iceberg — from the calving glaciers of Greenland and around the Davis Strait to Newfoundland’s Iceberg Alley. In The Berg, she traces that journey, revealing how ice seeds the ocean with nutrients, supports entire food chains and acts as a critical carbon sink for the planet.

But the making of this film carried a deeply personal dimension. Heinerth shot portions of The Berg just one week before undergoing cancer surgery. The documentary now bookends a transformative chapter in her life, framing both the vulnerability and resilience she experienced during treatment.

In our conversation, Heinerth shares how her “explorer mindset” helped her navigate cancer, just as she approaches diving beneath unstable ice: prepare, visualize, understand the risks, and lean on her team. As her great uncle once told her: “You alone can do it, but you cannot do it alone. That philosophy of courage and community guided her through radiation therapy and recovery.

We also dive into what it’s like swimming beside and beneath an iceberg, the physics of mixing fresh and saltwater, the explosive (and dramatic) end of an iceberg’s life, microscopic extremophiles and what they might teach us about medicine, and the new, under-ice research happening across Canada’s waterways. 

Heinerth also reflects on working with filmmaker James Cameron, whose relentless drive to explore the oceans has deeply inspired her. And when asked about her favourite exploration film, she points to the book Touching the Void, the harrowing true story of climber Joe Simpson. For Heinerth, it captures the raw psychology of survival: determination, dark humour, impossible odds, and the thin line between life and death that explorers understand all too well.

Heinerth is once again taking part in the Canadian Geographic Polar Plunge, raising funds for Canadian Geographic education programs, expedition grants and storytelling initiatives.

Support Heinerth, or sign up and plunge yourself: https://rcgs.org/polarplunge2026

Heinerth is the inaugural Explorer-in-Residence of the Royal Canadian Geographical Society and one of the world’s foremost underwater explorers. A pioneering cave diver, filmmaker and bestselling author of Into the Planet, she has led expeditions to some of the most extreme environments on Earth, including Antarctica’s icebergs to deep submerged cave systems. With more than 8,000 dives to her credit, Heinerth serves as the “hands and eyes” for scientists in remote underwater environments, translating complex research into powerful storytelling that connects global audiences to fragile ecosystems. Her work blends exploration, conservation, science communication and an unwavering belief in the power of community.