Some of us have been feeding advice to DARPA's ACTUV sub-tracking drone project for more than a year, but we haven't had a in-depth look at how the autonomous ship will go about its business, especially when chasing very silent diesel-electric subs. Thankfully, craft designer SAIC has stepped in with a detailed video tour. If there's suspicions that a diesel sub is in the area, the US Navy can deploy sonar buoys that give the ACTUV an inkling of where to go first. After that, the drone takes over with both long-range and short-range sonar. The vehicle can gauge the intent of ships in its path (with human failsafes) and hound a target for up to 13 weeks -- either letting the Navy close in for an attack or, ideally, spooking the sub into avoiding conflict in the first place. While ACTUV won't hit the waves for years, there's a promise that we'll always know about underwater threats and deal with them on our own terms.