Deep-submergence vehicle
A deep-submergence vehicle (DSV) is a deep-diving manned submarine that is self-propelled. 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.
Deep-submergence vehicle-1