Photos: This boat swims like a dolphin

A snorkel provides air to the engine--meaning that when the Angel is fully submerged, it begins to lose power, hence the short duration of the underwater travel.

"The engine draws such a vacuum during these dives that cockpit air pressure will lower to the point where it often pops the pilot's ears," Innespace's FAQ says. The cockpit does stay dry inside, the company says.

Photo by Innespace