Hollywood director James Cameron is on the point of attempting a dive to the bottom of the Mariana Trench on the western Pacific - the deepest place on Earth.
His team is waiting for clear weather and preparing for the seven-mile dive in Deepsea Challenge, a joint scientific project with the National Geographic Society and Rolex.
It'll be the first extensive scientific exploration by a manned vehicle to the Mariana Trench's lowest point, the Challenger Deep, where Cameron plans to spend six hours collecting samples for research into marine biology, microbiology, astrobiology, marine geology and geophysics.
The expedition is being filmed in 3D, and can be followed here.
The team's already successfully carried out field tests off the coast of Papua New Guinea, including a five-mile dive.
"The deep trenches are the last unexplored frontier on our planet, with scientific riches enough to fill a hundred years of exploration," says Cameron.
"Our goal is to build a scientific legacy for generations to come. It's also to inspire people across the globe to celebrate exploration and to explore with us online and through the media we produce."
There's only been one manned descent to the Challenger Deep, back in 1960, when US Navy Lt. Don Walsh and Swiss oceanographer Jacques Piccard spent about 20 minutes on the ocean floor.
A Rolex was taken on that trip; and for Cameron's dive there'll be a new experimental wristwatch, the Rolex Deepsea Challenge, strapped to the sub's manipulator arm.
Cameron really got the diving bug while working on Titanic, when he took 12 dives to the wreck. He subsequently formed Earthship Productions, which develops films about ocean exploration and conservation.
He's since led six expeditions, authored a forensic study of the Bismarck wreck site and done extensive 3D imaging of deep hydrothermal vent sites along the Mid-Atlantic Ridge, the East Pacific Rise and the Sea of Cortez.
The Deepsea Challenge expedition will be the subject of a 3D feature film which will appear in movie theaters and then on the National Geographic Channel.