The seas are looking rough. The U.S. has demanded the return of an unmanned underwater drone seized by a Chinese warship. According to the Pentagon, the unarmed U.S. Navy glider drone was collecting unclassified scientific data in international waters in the South China Sea when a Chinese warship approached and picked up the 10-foot device – despite radio messages from the American oceanographic vessel trying to pick it up themselves. The drone was reportedly testing water salinity and temperature. The Chinese have not yet responded to a formal diplomatic complaint from the U.S.