Texas A&M’s prototype unmanned underwater vehicle, being developed for the U.S. Navy, propels itself by wiggling like a fish. Metal muscles made of alloys that remember shapes are connected to evenly spaced vertebrae and shrink and expand as much as 8 percent as they’re alternately heated and cooled, causing the 3-foot sub’s sectioned hull to bend and flex. The result: No ripple evidence on the surface of the sub’s presence, making it much quieter than today’s vessels. A production version of the sub, at least three years off, could be as long as 13 feet and would be used for underwater reconnaissance (such as explosives detection) or exploration (ocean mapping). Popular Science article here.