A state-of-the-art unmanned warship designed for autonomous naval missions has been spotted in waters off of Washington state.

The USX-1 Defiant was being pushed by tug boat earlier this week through the Saratoga Passage in Puget Sound, just a few miles from the U.S. Navy’s Naval Air Station Whidby Island, according to The War Zone.

The 180ft, 240-ton unmanned surface vessel, a type of drone, was completed last month after a five-year development.

It has been constructed as part of the Defense Advanced Research Projects Agency’s “No Manning Required Ship” program alongside private maritime and operations company Serco – the primary contractor for the Defiant.