Not content to take tourists into space, Virgin’s Richard Branson on Tuesday unveiled a winged submarine that he plans to use for the first manned missions to the deepest ocean trenches.

Mr. Branson said he plans to pilot the 6-metre craft himself after fellow explorer Chris Welsh takes it down to the 12,000-metre deep Mariana Trench.

“The last great challenge for humans is to explore the depths of our planet’s oceans,” said the flamboyant entrepreneur when he introduced the carbon fibre and titanium craft at the Newport Harbour Yacht Club.

The 17-million-dollar submarine was originally commissioned by adventurer Steve Fosset, who died in 2007 in a plane crash as he was searching for a site on which to challenge for the world land speed record.

Mr. Branson, who made millions of dollars with Virgin Records before branching out with airlines and space tourism firm Virgin Galactic, said he hoped the craft would set as many as 30 world records. But his foremost motivation was to “educate the world about secrets hidden in its depths,” to make scientific discoveries and catalogue new species, as well as to open the ocean to deep-sea tourism.

“Great businesses can come from great challenges,” Mr. Branson said. “We believe there are thousands of people who would like to experience oceans, and become aquanauts.”