The long sleek body of a kayak makes it highly efficient at slicing through the water, but for unexperienced paddlers it also makes it easier to flip than a canoe. And that can be a terrifying experience, unless you're on the water in Olivier Feuillette's Subo which transforms from a kayak to a fully sealed submarine in just seconds.

A hinged hatch seals the kayaker in so they stay completely dry, while an oxygen tank provides all the O2 needed for an underwater voyage. And for longer dives a CO2 filter can also be used to extend the Subo's air supply for two to three hours. Of course with the hatch sealed the kayak's paddle is useless underwater, so an extended fish-like rudder takes over during a dive, gently swaying back and forth to provide propulsion. It's no Red October, but it beats goggles and a nose plug for exploring the murky depths around your cottage. [YouTube via Damn Geeky]