The UK Special Boat Service, an equivalent of the U.S. Navy SEALs, to receive three SEAL Delivery Vehicles (SDV) MK XI Shallow Water Combat Submersibles (SWCS). 

On 20 September, the U.S. State Department has made a determination approving a possible Foreign Military Sale to the United Kingdom of three MK XI SWCS for an estimated cost of $90 million.

The Government of the United Kingdom has requested to buy three SDV MK XI SWCS.  Also included are spares; handling equipment; test equipment; operator manuals and technical documentation; U.S. Government and contractor engineering, training, technical, and logistical support services; and other related elements of logistics and program support.

The proposed sale of the SDV MK XI SWCS will continue UK’s maritime partnership, interoperability, and regional security capability.  The UK has a proven track record of successfully deploying predecessor system.  The UK will have no difficulty absorbing this system into its armed forces.

The MK XI is a next-generation manned submersible and a type of swimmer delivery vehicle used to deliver special forces and their equipment for special operations missions.

The vessels have Doppler navigation systems, sonar, and docking systems that reunited the unit with its host submarine once its occupants have filed out. A dry dock shelter lets soldiers move from the sub to the water, then get into the vessel

Propulsion comes from a lithium polymer battery that gets it to a top speed of 4 knots, or just under 5 mph.

According to the H I Sutton, the MK XI min-submarine accommodate a crew of 6+.