A British Trafalgar class nuclear attack sub (SSN), preparing to head for a tour of duty in the Persian Gulf, honed its navigation and intelligence skills by maneuvering underwater until it was nearly stationary, and only a few meters (10-15 feet) below the keel of a Type 23 frigate. These frigates displace 4,200 tons and have a draft of 7.3 meters (24 feet.) That puts the 5,200 ton SSN about 12 meters (37 feet) beneath the surface, with its sensors checking out the bottom of the frigate. In this way, subs can collect useful information on how enemy ships are designed, built and maintained. Unlike the Americans, the British are more willing to discuss what their nuclear subs are up to, so more details of training exercises are let out.