This pedal-powered hovercraft, built by a flight group at the University of London, is constructed out of the absolute lightest materials possible (carbon fiber, glass cloth, styrofoam) to make it floaty enough to cross the Thames. And it does!
It's a pretty impressive little bit of engineering, even if steering looks super awkward and clumsy. Apparently the glass cloth used to cover the styrofoam is quite delicate as well, suffering damage just from accidental handling. But it's a pedal-powered hovercraft! [Steamboat Willy via MAKE]