Graham Hawkes, inventor of the "underwater plane," made his debut at the Monaco Yacht Show last month in a bid to entice billionaire boat owners to take the plunge.
"This is literally like flying underwater," said Hawkes, a U.K.-born ocean engineer who has spent decades designing cutting-edge diving suits and submarines. "Once you've done that, you don't want to do anything else."
Hawkes was one of four submarine vendors attending the Monaco show — one of the world's top yacht gatherings — for the first time, hawking multimillion-dollar high-tech wizardry they say makes perfect accessories for the wealthy.