And, Cameron added, he's an atheist.
Cameron's plan for the deeper dive depends on calm weather and pinpoint timing to conserve battery life. In 1960, Walsh and Piccard took nearly five hours to reach the bottom.
Cameron said his plan "is to scream to the bottom as fast as possible, then work at the bottom with all lights blazing." His descent in the dark, slightly-above-freezing water will only take 90 minutes and technically there's enough life support for a 56-hour dive. Cameron won't say how much the expedition costs.
While it may seem desolate — it's too deep for traditional fish to survive because of the pressure — there is life. Ravenous little shrimp-like creatures, sea anemones, worms with bristly feet, and sea cucumbers live in this section of the trench called Challenger Deep, said scientists on the Nereus team at Woods Hole.
"Exploring the trenches is a view back in time because they are so isolated from the ocean and circulation," Woods Hole submersible chief Bowen said. "It's inevitable that it's going to reveal something about the biological history of the planet."
Back when Don Walsh, now 80, took the plunge, he and Piccard saw sparkly tiny fish in the dark that glowed like light reflecting off snowflakes. He could hear sea animals outside. But once the ship landed and caused a dust-up in the fine flat oatmeal-colored bottom, he could see nothing.
"It was like staring into a bowl of milk," said Walsh, who is in Guam with the Cameron expedition.
Cameron won't be alone in trying to follow Walsh. But the next up is likely to be Branson. His company last year bragged that it's been to all seven continents and is going into space, so a $17 million sub venture is the next logical step. Google founder Schmidt is helping fund a $40 million effort by California-based DOER Marine to work on a more science-oriented human deep sea sub that is at least two years away. Also said to be in the hunt is Triton Submarines in Florida, a firm with no celebrity connection.
While some people call this "a race to the bottom," DOER Marine's president Liz Taylor said this is far more collegial.
"What we really have is a race against time in terms of what humans are doing to the oceans," Taylor said. Oceans provide most of the world's oxygen.
"Basically it's our planetary life support system at stake," she said, "and we're treating it as a supermarket and sewer at the same time."
James Cameron and National Geographic's Deepsea Challenge site:
NOAA's animation of diving into the Mariana Trench: http://bit.ly/AxD364
Branson's Virgin Oceanic: http://www.virginoceanic.com/
DOER Marine: http://www.doermarine.com/
Triton Submarines: http://tritonsubs.com/
Woods Hole Oceanographic Institution's Nereus sub: http://www.whoi.edu/main/nereus
Follow Seth Borenstein at http://twitter.com/borenbears