GWEN IFILL: Finally tonight, a voyage deep into the sea.
A famous filmmaker and explorer made that journey yesterday to the bottom of the Pacific, a place known as the Mariana Trench's Challenger Deep, some 300 miles Southwest of Guam.
Tom Clarke of Independent Television News has the story.
TOM CLARKE: He's behind the two highest-grossing movies of all time, but this was James Cameron's most ambitious production yet.
MAN: Above all, have fun.
JAMES CAMERON, filmmaker: Have fun, exactly.
TOM CLARKE: He set off in the middle of the night, but it makes no difference when you're heading to the darkest place on Earth. Once in the water, the sub turns vertical to drop like a torpedo to the bottom.
Sinking like a stone, it still took James Cameron two-and-a-half-hours to reach the bottom. His descent took him straight past the depth of the English Channel at just 180 meters. He wasn't even halfway when he passed the depth of the Titanic at 3,700 meters. That's more than two miles.
And his journey into the abyss even took him beyond the height of a submerged Everest, before he finally reached the bottom of the trench, 11 kilometers, nearly seven miles deep. He was three hours at the bottom and an hour coming back.
So what exactly did the film director see? Well, you will have to wait for the 3-D movie being released some time in the near future. But the ocean's deepest spot might not be a blockbuster.
MAN: You did it, man!
JAMES CAMERON: We all did it.
This is a vast, you know, frontier down there that's going to take us a while to understand that -- the impression to me was that it was a very lunar, very desolate place, very isolated. My feeling was one of complete isolation from all of humanity.
TOM CLARKE: It may be featureless, but these videos from British researchers using robotic subs have recently revealed remarkable animals, like these snailfish on a giant shrimp-like arthropod from four miles down. Who knows what Cameron's team might find.
JON COPLEY, marine biologist, University of Southampton: There's always a very good chance of new species. We have already heard that Jim Cameron has seen some sea cucumbers down there, very small ones. So it will be fascinating. He is going to go back and collect some samples, we hope. We should get to see what is down there.
When we're deeper than two miles -- and that's more than half our planet is covered by water that is two miles deep -- there's a 50-50 chance that we find new species.
TOM CLARKE: James Cameron admits diving the Mariana Trench is a boyhood dream fulfilled. What lurks beneath captured the public's imagination ever since that record dive in 1960.
And now it's attracting some other big fish too. Richard Branson and Google's Eric Schmidt are now building deep-diving subs as well. The abyss, so far James Cameron's private domain, is about to become the new frontier, provided you're rich enough.
GWEN IFILL: In addition to the 3-D movie, Cameron plans to direct a National Geographic special using the footage he gathered in yesterday's deep dive.