The Navy’s secretive sub-hunting ghost ship, technically known as the Medium Displacement Unmanned Surface Vessel, Sea Hunter, recently found its way into the record books as the first unmanned vessel to successfully traverse the open ocean between San Diego, California and Pearl Harbor, Hawaii.

At 132-feet long and boasting a displacement of 140 tons, the Sea Hunter is no undersized drone. The ship was purpose-built to hunt down encroaching submarines using the unblinking eyes of its on-board sensor suite–and to do so without the assistance of any human beings. The ship was first developed by the Defense Advanced Research Projects Agency, better known as DARPA, before being turned over to the Navy, which made the program’s ongoing efforts classified earlier this year.

However, despite elements of the Sea Hunter unmanned vessel remaining behind the veil of government secrecy, that didn’t stop the Navy’s lead contractor on the program, Leidos, from bragging about the vessel’s unique accomplishment last week.

“The Sea Hunter program is leading the world in unmanned, fully-autonomous naval ship design and production,” said Gerry Fasano, Leidos’ Defense Group president. “The recent long-range mission is the first of its kind and demonstrates to the U.S. Navy that autonomy technology is ready to move from the developmental and experimental stages to advanced mission testing.”

This successful voyage is an important milestone in the Sea Hunter’s development. In practice, the Sea Hunter would likely serve alongside a fleet of identical drone ships tasked with crisscrossing areas of open water that are likely to see enemy submarine activity, which means more often than not, the Sea Hunter would likely see use as a littoral combat vessel that can most often be found hugging the shoreline as a means of perimeter defense. It has now demonstrated, however, that these vessels can be sent to distant locations without the need to assign a crew to manage the long-duration voyage.

A crewed vessel did accompany the Sea Hunter throughout the trip, even occasionally boarding the autonomous ship to check on the status of operational systems–but according to reports, they did not conduct any repairs or make any system changes throughout the duration of the voyage.

This victory for the Sea Hunter program comes alongside the announcement that Leidos has been awarded $43.5 million to continue development on the Sea Hunter II, a sister ship that will incorporate changes based on lessons learned through the Sea Hunter’s ongoing trials.