British billionaire Richard Branson unveiled plans Tuesday to pilot a "flying" mini-submarine down to the furthest depths of the oceans, in his latest record-breaking adventure.The single-seater Virgin Oceanic craft will try to reach the deepest points in each of the world's five oceans -- in what would be the first such feat -- starting with the deepest of them all, in the western Pacific later this year.
"With space long ago reached by man, and commercial spaceflight tantalizingly close, the last great challenge for humans is to reach and explore the depths of our planet's oceans," said Branson.
