Deep-submergence vehicle

A deep-submergence vehicle (DSV) is a deep diving manned submarine that is self-propelled. The term DSV is generally one used by the United States Navy, though several navies operate vehicles that can be accurately described as DSVs. DSVs are commonly divided into two types: research DSVs, which are used for exploration and surveying, and DSRVs (Deep Submergence Rescue Vehicle), which can be used for rescuing the crew of a sunken navy submarine, clandestine (espionage) missions (primarily installing wiretaps on undersea cables), or both. DSRVs are equipped with docking chambers to allow personnel ingress and egress via a manhole.