When Mercedes-Benz began to contemplate its next generation of high-efficiency small cars, it sought aquatic inspiration. But instead of considering obvious undersea hot rods like sharks, the Mercedes team turned to a fish that resembled a car: the tropical boxfish. A native of the Indo-Pacific region, the Ostracion cubicus is surprisingly slick. Wind-tunnel testing of a clay model revealed a drag coefficient (Cd) of just 0.06, startlingly close to the ideal 0.04 of a water droplet.