The Turtle and the Robot : Image

Undersea vehicles can’t turn on a dime—Seals swimming fast at 2.4 meters per second need only one-tenth of their body length to turn completely around, in the face of an oncoming coral reef, for example. Like seals, the robot Finnegan has “flippers” (flapping foils). It can’t turn as fast or deftly as a seal, but it is more maneuverable than vehicles such as REMUS, which use conventional screw propellers for propulsion. (Illustration by Jack Cook, Woods Hole Oceanographic Institution)