The trouble with making a documentary about the deepest, most remote place on the planet, five miles below the surface of the ocean, is that there really isn't a whole lot happening down there. There are no monsters, no sunken alien warships, just an endless, featureless expanse. But even this is more compelling, in its way, than watching James Cameron get into and out of a tiny metal sphere several times over the course of a ninety-minute film about his seven-year-long journey to get down there, to Challenger Deep, the bottom of the Mariana trench, a place that had only been visited by humanity once before, fifty-two years prior.

On Monday, the American Museum of Natural History held a special screening of the film Deepsea Challenge 3D, which Cameron executive produced. In the film's introduction, Cameron describes his life-long obsession with the sea, and especially the unexplored ocean floor. "There's a dark continent down there," he says in a voiceover. (Hmm.) If Cameron had his druthers, it seems as though he'd be perfectly happy by himself, in a cramped, metal sphere thousands of feet below the surface of the sea, looking at jellyfish. "Am I a filmmaker who does exploration on the side?" he asks the camera at one point. "Or am I an explorer who does filmmaking on the side?" Cameron has, since filming The Abyss twenty-five years ago, pursued a side-career as a deep-sea adventurer, organizing and leading expeditions not only to the RMS Titanic (twice) but also to the German battleship Bismarck and other points of historical and oceanographic interest.

The core team that worked on the Deepsea Challenge—this is the name of the expedition, the name of the submarine is the Deepsea Challenger, and the name of the part of the Mariana trench at which the dive took place is called the Challenger Deep—was initially assembled for Cameron's second expedition to the Titanic wreck. It's a large group of people. But we never really learn much about them other than that they are sad when James Cameron is mad.

After yesterday's "Special Youth Screening," questions from the audience were moderated by Frederick P. Rose, director of the Hayden planetarium, and famous space scientist Neil deGrasse Tyson. One young man named James asked, "Would you want to go back and bring people with you?" This was an astute question, as so much of the film involves cameras pointing at Cameron while he reacts to things underwater. "Well, I'm not alone when I bring the story back, when I bring the images back," he said. "That was really important for me so I could bring the story back and share it with everybody here." Cameron hopes one day to be able to live-stream such expeditions using fiber optics so that whole audiences can travel with him.

The "symbolic value" of the film, Cameron said, is much greater than the actual, scientific accomplishments of the expedition. "It shows us what we don't know; it shows us what our capability is." Until recently, there were only two ships in the world that could reach the most remote parts of the ocean. One of them, Deepsea Challenger, is functional, but currently offline. (It was sitting on the curb outside of the museum.) The other imploded in the Kermadec trench. "That's kind of a ridiculous situation for the U.S. to be in, for human civilization to be in," Cameron said. "We actually can't go to an area of the surface of our planet that is the size of North America. We don't have the equipment to go there."

These regions include subduction zones, areas where one tectonic plate is pushed under another—a violent process that generates the forces which turn into tsunamis. We know that this is where this process, which causes so much death and destruction, starts, Cameron said, but we don't have the means to do anything about it: "There's nothing. There's nothing that can go down today and place a set of connected instrumentation, which is the only way you're going to get real-time data on seismic swarms that can give you some chance at generating a predictive model." (This part of the conversation was where Cameron really hit his stride. He is much more compelling as an advocate for science and exploration than as an on-screen scientist and explorer, more Steve Zissou than Jacques Cousteau.)

"I'm tired of talking to Senate subcommittees about funding and all of the other things we have to do," Cameron said, gesturing to Tyson. "It's a waste of time." He continued, "People believe we're in a kind of post-exploration age here on earth. They think of the oceans as having been explored, and they haven't. And they think of space, you know, we've been told since the mid-sixties, space is the final frontier. They don't understand there's a frontier here on earth."

Brendan O'Connor is a reporter living off the L train.

Photo by Mark Thiessen/National Geographic of James Cameron emerging from the DEEPSEA CHALLENGER submersible after his successful solo dive to the Mariana Trench.