It may be good to be the prince...

...but sometimes the prince is crazy...

William Broad has the story in The New York Times:

For centuries, the daredevils known as submariners have slipped beneath the waves in vehicles made for horizontal travel. Their craft are basically underwater ships. Even submersibles, small vessels that dive unusually deep, follow the horizontal plan. Until now.
In a stroke, James Cameron has upended the field, literally and figuratively. A man known for imaginative films (Titanic and Avatar), he has reinvented the way that people explore the deep ocean.
This month, Cameron unveiled his unique submersible and announced plans to ride it solo into the planet’s deepest recess, the Challenger Deep in the western Pacific, nearly seven miles down.
He calls it a vertical torpedo. The axis of his 24-foot-long craft is upright, rather than horizontal, speeding the plunge. His goal is to fall and rise as quickly as possible so he can maximize his time investigating the dark seabed. He wants to prowl the bottom for six hours.
“It’s very clever,” said Alfred S. McLaren, a retired Navy submariner who helps to run a company that makes submersibles. “Nobody has done this kind of thing before. It’s a great idea, a tremendous idea.” He likened Cameron to “an underwater Steve Jobs: difficult to get along with but very creative. He’s driven,” Dr. McLaren went on. “He put together a hell of a technical team.”
Just as bullets are spun to steady their flight, Cameron’s craft rotates on its vertical axis; another first. In a test dive, he has already broken the modern depth record for piloted vehicles, going down more than five miles.
“He’s done something radical,” said Peter Girguis, a biological oceanographer at Harvard and head of a panel that oversees the nation’s fleet of deep-research vehicles. “He’s set aside the conventional wisdom.”
Cameron sees his craft (built in secrecy in Australia over eight years) as greatly expanding the power of scientists to explore the abyss. On the Challenger Deep expedition, he is working with the National Geographic Society, the Scripps Institution of Oceanography, the University of Hawaii, and other scientific groups.
“It’s really fun,” he said in an interview during sea trials off Papua New Guinea. “There’s no bigger high in my world.”
Cameron, now near the Challenger Deep in the expedition’s ship, is awaiting calm seas for what experts called an audacious bid that will shed light on a hidden world of strange life forms.
The deep sea is much harder to explore than outer space. Far from the sun’s warming rays, the inky darkness miles down hovers at temperatures near freezing. Seawater is also corrosive, often full of debris, and largely opaque to light and radio waves.
Most daunting of all, it is extraordinarily heavy. In the Challenger Deep, the waters overhead exert a downward pressure of more than eight tons per square inch. Typically, submersibles fight the extremes with bright lights and cramped personnel spheres, a shape that can best resist crushing pressures. Explorers dress warmly and communicate with mother ships on beams of sound. They peer out of tiny portholes that are extraordinarily thick.
Until now, the world’s most advanced submersibles were built by governments. They can go as deep as 2.8 miles (the United States), 3.2 miles (China), 3.7 miles (France and Russia), and 4 miles (Japan). All follow the horizontal plan; most look like squat submarines with large tail thrusters.
Cameron plans to plummet 6.8 miles. The Challenger Deep is the most remote area of the Marianas Trench, the deepest of the seabed recesses that crisscross the globe. He will cram his 6-foot-2 frame into a personnel sphere just 43 inches wide, forcing him to keep his knees bent and his body largely immobile. The dive plan calls for him to remain in that position for up to nine hours.
People descended to the Challenger Deep just once before, in 1960, when the United States Navy sent down two men. They stayed twenty minutes. (By contrast, a dozen men have walked on the moon and spent more than a collective eighty hours exploring its surface.)
While the most striking feature of Cameron’s vehicle is its vertical axis, it innovates in other ways, according to ocean experts and National Geographic, which is a sponsor of the expedition. (Its website details the advances.)
For instance, the twelve thrusters are mounted above the crew capsule, keeping the muddy seabed largely undisturbed. Cameron wants no repeat of the 1960 experience, in which the craft’s landing stirred up so much ooze that the divers could see little during their stay on the bottom and took no pictures. After his five-mile test dive, he wrote that propeller wash from the thrusters barely “kissed” the bottom, forming silken tendrils that undulated and hung “like ectoplasm”.
A bigger advance centers on the craft’s structural foam. It counteracts the heavy weight of the steel personnel sphere and keeps the craft buoyant and able to rise quickly (once weights are shed). Cameron and his team were forced to develop their own superstrong foam after commercial varieties failed under crushing test pressures.
“From a sub builder’s perspective, that’s a huge breakthrough,” said Phil Nuytten, president of Nuytco Research, a leading maker of undersea robots and submersibles. Dr. Nuytten praised Cameron’s small personnel sphere as “a big innovation” that greatly reduced the need for buoyant foam and reduced the craft’s overall size. By contrast, the spheres of conventional submersibles are much larger and heavier. “The benefit is enormous,” he said. “You dramatically lower weight as the sphere size decreases.” In an interview, Nuytten said he had long worked with Cameron; their relationship goes as far back as The Abyss in 1989, when the director first displayed a fascination with the deep sea.
And while Cameron may be better known for his movies than for his undersea dives, he is anything but a dilettante, Nuytten said, adding: “Very few people realize that he’s a very good technologist. This is Jim’s design. It’s his baby from start to finish.”
Dr. Girguis, the Harvard oceanographer, said the debut of the new submersible suggested that deep exploration was entering a new phase of ambition. “Eighty percent of our biosphere is the deep ocean,” he said in an interview. “The time is right to push the envelope, not only with respect to technology but our understanding.” 

Rico says this is another adventure that he'll sit out, thank you very much... (Though he's sure the IMAX movie will be fascinating.) But Rico recalls his grade-school teacher Mrs. Tate, back in 1960, a woman from Louisiana, whose heavily-accented pronunciation of Marianas Trench was memorable... (And this thing is "forcing him to keep his knees bent and his body largely immobile. The dive plan calls for him to remain in that position for up to nine hours"? Sounds like he could be ripe for a thrombosis, if he's not careful...)