• Filmmaker James Cameron

    Filmmaker James Cameron regularly pilots subs. (Photo: Charlie Arneson)

Wedged into an icy-steel sphere, hurtling through the pitch-black depths, profoundly alone and exquisitely vulnerable, James Cameron made history when he reached the absolute bottom of the ocean on March 26, 2012.

That morning he became the first solo voyager to the Mariana Trench in the Pacific Ocean — specifically the Challenger Deep, at 11 kilometres the lowest part of the trench — and the only human to spend three hours driving a submersible around the trench’s floor collecting scientific data.

It ranks as one of humanity’s boldest and most dangerous feats of exploration, and is only the second time human eyes have seen the very bottom of the sea. It was also the culmination of Cameron’s lifelong passion for being underwater.

“It’s some combination of the actual tactile experience of it and a sense of exploration, the exhilaration of seeing something new, of being in another world, having a solitary experience that’s meaningful in some deep psychological way,” he says, recalling his first open-water scuba dive at 16, in Ontario’s Chippawa Creek with a rope tied around his waist and his father holding onto it on the pier. “And the idea that we’ve got a universe to explore, a vast ocean to explore, that there are going to be wonders there.”

The Mariana Trench was a little more dangerous than the Chippawa Creek. With 1,146 kilograms of pressure for every square centimetre of the sleek vessel’s surface, Kapuskasing, Ontario-born Cameron knew that any minuscule breach of the hull at that depth would mean instant death.

“In a way, it’s more challenging than going into space,” says Susan Avery, president and director of Massachusetts’ Woods Hole Oceanographic Institution.

The only other two humans to have made the voyage travelled there together, and that was 52 years before Cameron. In 1960, U.S. Navy Lt. Don Walsh and Swiss oceanographer Jacques Piccard became the first to reach the Mariana Trench, hovering over it for 20 minutes before ascending.

Cameron, who is best known as the Oscar-winning director of the blockbusters Avatar and Titanic, spent seven years creating the Deepsea Challenger, a “really cool machine” that could withstand the harshest, most remote environment on the planet, collect film and samples, then bring its pilot back alive. He and his privately financed team of engineers — most of whom had not worked on a sub before — invented new pressure-resistant buoyancy foam and made advances in deepsea lighting, 3D cameras, robotic arms and packs of lithium-ion batteries.

Because he wants the innovations to spur further research, Cameron, who studied marine biology before becoming a filmmaker, donated the vessel to Woods Hole this summer after a cross-country United States show-and-tell tour aimed at children. Scientists have already begun analyzing the machine’s technological advances and Avery says they’ll be critical to new robotic designs.

More scientific advances are in the chute. Cameron and his team collected samples and 3D film during the Deepsea Challenger’s 13 test and research dives. Among the finds are 68 new species and counting, including a rich stew of deepsea bacteria that may offer clues to the origins of life.

But the main legacy may be what Cameron calls the “inspirational dividend” of accomplishing something so difficult and then carrying back the tale. He wants people to fall in love with the ocean and also protect it from dire human threats such as climate change. To that end, a 3D film about his voyage to the bottom of the sea will be in theatres in the coming months.

“Nothing would make me happier,” he says, “than if I could inspire a few kids to become explorers, engineers and scientists, and feel a sense of empowerment that their curiosity is actually a pathway to something worth committing their life to.”