Despite many developers' efforts to teach cars to steer themselves around roads filled with human drivers, pedestrians, and cyclists, the first great wave of autonomous vehicles may not arrive on land. Instead, it might follow the time-honored tradition of running away from tricky problems by heading for the open seas. Rather than worrying about robo-taxis, groups around the world are working on making ships--large and small--self-piloting, which could save fuel, prevent expensive accidents and groundings, and relieve crews of some of mundanity of life on the water. Let's start at the big end of the scale. Container ships and other behemoths may not have to deal with rogue scooters, but they come with their own challenges.