Robot fish are typically pale imitations at best -- even when they move quickly, they don't move all that gracefully. MIT's new soft robotic fish should be much closer to the real animal, however. Instead of relying on rigid joints and motors to swim, the new fish wiggles its tail fin by inflating a channel with carbon dioxide. The switch to pressure-based power results in not just more natural-looking movement, but the kind of explosive energy that you'd expect from an undersea critter; a strong CO2 blast will turn the robot 100 degrees in an instant. The current design is built more for speed than longevity, but MIT's researchers foresee a longer-lasting model that could follow schools of real fish and study them without drawing attention.