under new homeland security measures, boats must keep at least how many yards away from all military vessels and ships?

100 yards

Explanation:

According to the security measures, all of the boats have to keep a distance of at least 100 yards. Apart from keeping this distance, the boats are also commanded to slow down when they are within 500 yards distance from the military vessels and ships. The reason for this measures is so that the boats don't get in trouble, and so that the military doesn't see them as a danger, seeming to be not obeying orders, or look like they are aggressive.