At nearly 14 inches long, a new tuna-inspired robot created by University of Virginia researchers can flap its tail as fast as real tuna and swim at speeds up to 1.5 mph, or two body-lengths per second. In a new paper out in Science Robotics, the team behind this creation breaks down how they made this tuna-like robot – a machine that can tense up or relax its tail joint to move at different speeds. This mechanism has allowed the tuna bot to reach high speeds while also conserving energy, a method that could one day help improve swimming robots and even underwater vehicles.