Here is some more info from the Washington Post:
The trip is the first attempt by humans to reach the Challenger Deep, the deepest point of the Mariana Trench, since two Navy lieutenants touched bottom in January 1960. On that trip, Don Walsh and Jacques Piccard spent just 20 minutes on the bottom inside the bathyscaphe Trieste, the only humans before Cameron to visit the spot. The sub kicked up so much silt that the pair saw virtually nothing outside their porthole.
Cameron’s dive was expected to last about eight hours. According to plan, the innovative “vertical torpedo” — a lime-green submersible called Deepsea Challenger that Cameron helped design — was to plummet nearly 36,000 feet in just over 90 minutes, the swiftest deep dive with a human pilot. At the end of the dive, Cameron was to release 1,100 pounds of metal ballast, sending the vehicle shooting to the surface.
High-tech “syntactic foam” that forms the core of the vehicle was designed to be compressed by the immense pressures, while a metal sphere less than four feet across kept Cameron safe. The sphere is pressurized, so he was not at risk for decompression sickness.
An unmanned test dive Friday proved the sub worthy of surviving the crushing pressures of nearly eight tons per square inch — like an elephant standing on your toe.
Redundant safety systems were designed to release the vehicle’s ballast and send it toward the surface if problems arose. There was enough oxygen on board for 56 hours. And if the sub got stuck in bottom muck, ocean saltwater would eat through straps holding the sphere inside the vertical torpedo, releasing the ballast in about two days.
Four high-definition cameras recorded the trip for a television special and a 3-D theatrical film, with an eight-foot-tall bank ofhigh-intensity lights illuminating the depths of the trench, which lies far beyond the reach of sunlight. The Mariana Trench is a gash formed where one of the Earth’s huge tectonic plates, the Pacific plate, plunges under another, the Mariana plate.
Besides filming the journey, Cameron aimed to collect rocks, soil and any deep-sea creatures he encountered, using hydraulic arms attached to the sub. Biologists and geologists from the Scripps Institution of Oceanography and NASA will scrutinize the samples for exotic microbes and clues to how the slippage of the two giant tectonic plates can cause earthquakes and tsunamis.That would have been awesome if he had got stuck at the bottom of the world for two days... just saying...