It is the first robotic fish to contend with the currents and pressures of an actual ocean setting for an extended period of time. In a study published Wednesday in Science Robotics, the authors describe how SoFi can nimbly navigate a coral reef off Fiji in three dimensions, swimming up, down, left, right and forward, all at the behest of a diver armed with what looks like a Nintendo controller. The authors also report that the robot can handle water depths of about 60 feet, and appears to swim alongside real fish without spooking them. "For us, this fish is...