Today is christening day for DARPA's Sea Hunter, a full-scale prototype of an autonomous surface vessel that's designed to be able to launch from a pier and go out on its own for weeks or months at a time, for thousands of miles at a stretch. The 132-foot-long, diesel-powered vessel was built by U.S. defense contractor Leidos under DARPA's ACTUV program, a somewhat clunky nested acronym that stands for Anti-Submarine Warfare (ASW) Continuous Trail Unmanned Vessel. The ship, now a joint project with the U.S. Office of Naval Research, was originally conceived as a tracker of stealthy diesel-electric submarines, but it's a flexible platform. "What we've kind of realized over the course of the program is that it's a truck," program manager Scott Littlefield tells IEEE Spectrum. "It's got lots of payload capacity for a variety of different missions."