Crab robot. Ariel, a prototype landmine-clearing crab robot, seen by the harbour in Boston, USA. This 6-legged robot was designed to scuttle from the shore through the surf to search for underwater mines in the ocean. Its movement is based on studies of real crabs, with some improvements. When Ariel is knocked onto its back by a wave, it can re-orient itself and continue walking upside-down. Real crabs must flip themselves upright before moving off. However, Ariel cannot manoeuvre itself around large rocks. It was built by iRobot, funded by DARFA (Defense Advanced Research Projects Agency).