Dry deck shelter

A dry deck shelter (DDS) is a removable module that can be attached to a submarine to allow divers easy exit and entrance while the boat is submerged. The host submarine must be specially modified to accommodate the DDS, with the appropriate mating hatch configuration, electrical connections, and piping for ventilation, divers' air, and draining water. The DDS can be used to deploy a SEAL Delivery Vehicle submersible, Navy divers, or Combat Rubber Raiding Craft (CRRC).
Active and future DDS-capable submarines.
Royal Navy.
In UK service it is formally named the Special Forces Payload Bay (SFPB) and was procured under ‘Project Chalfont’
 To help reduce these risks, training is conducted at the purpose-built Chalfont Shore Facility (CSF) constructed by BAE Systems at HMNB Clyde. 
United States Navy.
The United States Navy's DDSs are long and high and wide, add about 30 tons to its host submarine's submerged displacement, can be transported by trucks or C-5 Galaxy airplanes, and require one to three days to install and test. They have three HY-80 steel sections within the outer glass-reinforced plastic (GRP) fairing: a spherical hyperbaric chamber at the forward end to treat injured divers; a smaller spherical transfer trunk; and a cylindrical hangar with elliptical ends. The hangar can support a SEAL Delivery Vehicle (SDV) submersible, six Navy SEALs to man the SDV, and a crew of Navy Divers to operate the DDS and launch the SDV; or 20 SEALs with four Combat Rubber Raiding Craft (CRRC). The SDV release team consists of 2 officers, 2 enlisted technicians, and 18 divers. 
The two SEAL delivery vehicle teams report to Naval Special Warfare Group 3.
There are currently six portable dry deck shelters in use by the USN, the first one built by Electric Boat. The first, designated DDS-01S ("S" for starboard opening outer door), was completed in 1982. The remaining five, DDS-02P ("P" for port opening), -03P, -04S, -05S, and -06P, were built between 1987 and 1991 and were built by Newport News Shipbuilding. The shelters are maintained by a combined effort of Navy divers stationed on the teams and workers of the maintenance company Oceaneering International. They have expected useful lives of about 40 years each.
The first submarine to have an operational dry deck shelter was the , which was fitted with the DDS in 1982 and first deployed with it in 1983.
Marine nationale.
Barracuda-class_submarine_(France)
Former DDS-capable submarines.
Former US Navy DDS-capable submarines include:
Five s were also fitted to carry the DDS.