Not that Cameron - James Cameron the film director. After waiting for the right conditions, he's at the bottom of the Mariana Trench. According to the story at the link (National Geographic), he'll be exploring for several hours before returning to the surface. There will be periodic updates.
Thought an alert here would be a good thing. Good luck to Cameron - this could be the first of several trips, and a possible model for future deep ocean manned exploration. No reason robots should have all the fun, though I don't think I'd like to spend hours in a sphere only 43 inches wide....
Updates below
8:58 PM PT: UPDATE: It has been reported he's returned to the surface - faster than expected, about 70 minutes.
UPDATE 2: Cameron has returned - more at the National Geographic.
After a faster-than-expected, roughly 70-minute ascent, Cameron's sub, bobbing in the open ocean, was spotted by helicopter and would soon be plucked from the Pacific by a research ship's crane. Earlier, the descent to Challenger Deep had taken 2 hours and 36 minutes.
Expedition member Kevin Hand called the timing of the DEEPSEA CHALLENGER sub's ascent "perfect."
"Jim came up in what must have been the best weather conditions we've seen, and it looks like there’s a squall on the horizon," said Hand, a NASA astrobiologist and National Geographic emerging explorer.
Before surfacing about 300 miles (500 kilometers) southwest of Guam, Cameron spent hours hovering over Challenger Deep's desert-like seafloor and gliding along its cliff walls, the whole time collecting samples and video.