A Thunderbirds-style military vehicle designed for unmanned, long-distance underwater missions has completed in-water testing. The Manta Ray prototype uncrewed underwater vehicle (UUV) completed the full-scale testing off the coast of Southern California over the last three months, according to manufacturer Northrop Grumman. Manta Ray was built through the U.S. Department of Defense's Defense Advanced Research Projects Agency (DARPA) program.