I’m on a boat. The boat does not float. At least not in the traditional sense. The manufacturer says somewhat enthusiastically that “it flies.” In reality it hovers two feet above the water, propped up on stilts attached to two horizontal carbon-fiber fins—hydrofoils—that slice through the waves, raising the hull clean out of the sea. Underwater, a torpedo-shaped, battery-powered propeller mounted along the rear foil thrusts all 1.6 metric tons of the Candela C-8 forward.