Deepsea Challenge 3
Credit: Mark Thiessen/National Geographic

You would think James Cameron would want to rest. The 59-year old behind the two highest-grossing movies of all time—Avatar and Titanic, in addition to all the technology required to make those films a reality—has earned himself the right to a leisurely retirement. But there’s no rest for his curiosity.

Cameron’s latest endeavor, Deepsea Challenge 3D, is indication that he will never stop exploring. “I’m just a very curious person, I guess,” Cameron said in a recent interview on EW Radio. “It’s what attracts me to science, to engineering. I like to build things and see if they work. I get as much of a charge out of building the machines as I do out of operating them.”

During the last seven years—and while he was still in production on Avatar—Cameron and his crew of seafaring men constructed a submersible capable of diving to the depths of the ocean, down 36,000 feet. He of course documented the entire experience, from the challenges they faced to putting together such a vehicle to the dives themselves in a documentary that will debut Aug. 8 in limited release.

The film is compelling, suspenseful, and very personal; Cameron’s director John Bruno added in tidbits of Cameron’s childhood to explore his subject’s lifelong passion for science. It’s also tragic: On the eve of the crew’s expedition, the film’s original writer/director Andrew Wight and Mike deGruy were killed in a helicopter accident on their way to film aerial shots of the submarine. “It was the worst day of my life,” Cameron said.

The crew continued with production, as a way to honor their fallen comrades, after quickly hiring Bruno to take over. And it was Bruno’s idea to add in re-enactments of Cameron’s childhood as a way to personalize the film and contradict the chatter on the Internet, after Cameron made his dive to 28,000 feet.

“We got some feedback over the Internet that this was a stunt and it made me mad,” said Bruno, who has worked with Cameron on his films—and his dives—for the past 27 years. “I changed the course of my interviews, and I thought we should do a reenactment of him in 1960 as a kid and with his experiments on white rats. I don’t think the public was aware [of his dedication to science].”

As the film showcases the fits and starts of the laborious process to get the DeepSea Challenger ready for 36,000 feet, Cameron, the diver, is pictured dealing with mechanical frustrations, electrical malfunctions, and other setbacks. Was he ever afraid?

“Generally speaking, I’ve had hair-raising experiences in subs over the years and I don’t panic,” he says. “If there is fear, it’s beforehand, the night before or a couple days before. Thinking about what’s coming up, and that there is always some X factor out that that no matter how many years you’ve thought about this problem, there might be something you haven’t thought of.”

But when he’s being bolted into the submarine and hoisted into the water, the only emotion he experiences is excitement. “I get what astronauts call ‘Go Fever’ and I just want to go. It takes something pretty drastic before I will cancel the dive once we’re in process.”

Now, Cameron has turned his attention back to the Avatar sequels, which he is currently in deep pre-production on. Due out Christmas 2016, Cameron seems a little iffy that he’ll make the date: “I find deadlines to be entertaining,” he says with a laugh. “In the engineering community they are considered ‘notional.’ Reality has a tendency to intrude.”