In the village of Ruraï, in Papua New Guinea, people tell of a water hidden deep within the Nakanai Mountains so pure that anyone who drinks it is said to gain extraordinary powers.

Immersed in the heart of a tropical rainforest, a team of cavers - including the inimitable Cédric Lachat - sets out to uncover this mysterious underground river system. Their goal is to reveal what nature still keeps hidden, in order to better protect it.

A committed adventure at the edge of the world, in the depths of a jungle that slowly and relentlessly wears you down. Will it succeed in breaking the spirit of this fearless expedition?

Director Biography - Alex Lopez

Alex Lopez is a film director and cinematographer. Trained as a film editor, he gradually specialized in adventure and exploration documentaries, filmed in immersion within demanding natural environments.

A practitioner of vertical sports, he develops work focused on wild territories and underground worlds. He directed One Degree (2022), about athletes’ environmental engagement, followed by On a marché sous la terre (2023), a film widely awarded at international adventure and mountain film festivals.

He continues this work today through documentaries that combine exploration, science, and the relationship between humans and nature.

Director Statement

My work as a filmmaker is deeply influenced by my experience as an explorer and by my fascination for natural environments that remain largely unknown. Through my films, I seek to bring audiences into places that are rarely seen, and to share the sense of discovery that accompanies exploration.

Water has always been a central theme in my work. In many parts of the world, it is both a vital resource and a fragile element within complex natural systems. In the Nakanai Mountains of Papua New Guinea, water disappears beneath the tropical forest to form immense underground rivers that shape the landscape and sustain the surrounding ecosystems and communities.

With Secret Rivers of the Nakanai, I wanted to follow this invisible journey of water and explore the relationship between humans and their environment. The film brings together explorers and local communities whose knowledge and daily lives are closely tied to these mountains. Their stories reveal how exploration, science, and traditional knowledge can contribute to a better understanding and protection of these unique natural systems.

More than an expedition film, this project is also a reflection on the fragile balance that connects forests, water, caves, and the people who depend on them.