James Cameron tweets from the ocean floor (Update: Or did he?)

Titanic director James Cameron has just joined one of the most exclusive clubs on Earth, becoming just the third person to reach the deepest part of the ocean, and return safely to the surface. New information at the end of the post.

We took a look at his Deepsea Challenger submersible just a couple of weeks ago, at which point the trip seemed like it could happen at any moment.

Cameron becomes the first person to reach the bottom of Challenger Deep since a two man U.S, Navy expedition over 52 years ago. Don Walsh, the sole remaining survivor of the 1960 trip, called Cameron's support ship to congratulate him once he had returned safely to the surface.

Once he hit bottom, Cameron tweeted "Can't wait to share what I'm seeing w/ you." Unlike that first trip where they spent only 20 minutes on the sea floor, Cameron spent hours exploring the trenches, collecting samples, all while videotaping the whole thing using several cameras in high definition 3D naturally.

After a trip like that, you might think Cameron would take a few days off to chill. Not a chance; on Wednesday he's due in London for the premiere of Titanic 3D. I guess he's grateful that his Deepsea Challenger didn't end up permanently stuck on the bottom like that ship.

Update from The Editor: Turns out James Cameron's tweet wasn't really from seven miles under the ocean, as a lot of you surmised in the comments below. From Slate's Forrest Wickman:

"How do you tweet from the bottom of the ocean? The secret turns out not to be a killer service plan… but having a friend up on the surface. As a spokesperson for the National Geographic Society informed me, 'the tweet was pre-written by James Cameron and sent by a team member from the surface ship, with his knowledge, when he arrived at the bottom.'"

National Geographic, via Slashgear

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