James Cameron in Deepsea Challenge 3D (National Geographic Entertainment)

People often grow up fantasizing about  outer space and/or the Earth’s oceans, the two great canvasses available for boundless possibility and discovery. James Cameron is at the far end of the spectrum in both of these interests. He made one of the coolest deep space adventure movies ever with Aliens, and the documentary Deepsea Challenge 3D shows how deeply ingrained his curiosity with the ocean depths is. His career, in retrospect, seems very ocean-centered: The Abyss, Titanic, and reportedly the remaining Avatar sequels.

The Abyss, in particular, shows off his fascination with cutting-edge deep-sea exploration technology, an interest which is way beyond a hobby. Evidently he’s sunk a considerable chunk of his own vast fortune into the hardware to enable his trip to the deepest part of the Mariana Trench in the Pacific Ocean. With National Geographic footing some of the bill, serious man hours and resources were poured into this venture. His team created several technologies and all of the safety measures and strategies, facing the problems of pioneers in any area.

He built a real-life spaceship, painted it blaring green, and hired a dedicated crew of engineers and seamen to undergo a detailed plan of safety tests and retests. And retests and retests. Most of the movie covers the increasing higher level of trials—adjusting for equipment malfunctions or deployment errors—leading to the employment of a submersible capsule diving to 37,000 feet to the ocean floor. According to an assistant, Cameron’s personal nightmare is to be trapped in a tiny pod at the bottom of the ocean that is burning from within. Is there a more dangerous, deadly situation? Two naturally opposed powers, fire and the sea, joining forces to kill you? Yikes. (Spoiler: He doesn’t burn to death at the bottom of the ocean. There will be more Avatar movies).

One of the neatest things about the film is the inside look at how Cameron manages complex physical productions, which was a major part of directing the films Terminator 2: Judgment Day and, notably, Titanic. You see how hard he pushes people, how his team doesn’t always appreciate his intensity, but at the end of the day, they respect him. Directing massive $200 million movies requires commanding a small army, and you definitely see the qualities of a general come out. Cameron narrates the film, too, so there is a whole lot of James for you.

The overall message is that we need to start exploring outer space more seriously. Cameron demonstrates how someone, with considerable resources and skills, can plumb the depths of the ocean. (He makes sure to note that his Rolex wrist watch keeps ticking with 17,000 pounds of pressure per square inch crushing it.) We pretty well already knew what the bottom of the ocean would look like—empty, desolate, alien, kind of like the surface of the moon, but with water. But other planets? No idea. Much cooler.

The film closes with a voice-over imploring our species to keep its taste for exploration alive, while panning out over the planets of our solar system, then a nearby solar system, and so on, reminding us how we have barely scratched the surface of space. If one person can plummet to the ocean floor, then mankind working together should at least have colonized Mars by now.