London, United Kingdom — The Special Boat Service (SBS) will be getting new mini-subs from the United States.

After the budget announcements for the next year, the British government approved the purchase of three MK 11 Shallow Water Combat Submersibles (SWCS) to replace the ageing MK VIII Mod 1 Swimmer Delivery Vehicle (SDV). The SWCS are manned mini-submarines that can hold up to six operators and their equipment. They can be launched and recovered by both surface warships and submarines that are fitted with the necessary dry dock shelter (DDS) apparatus. SWCS can also be attached underneath a helicopter.

SDVs are used to clandestinely transport operators to their target. The U.S Navy SEALs also use the SWCS. They can remain underwater for many hours and can avoid most detection systems. The use of midget subs and SDVs goes back many decades. During the Second World War, Italian frogmen utilised SDVs to successfully attack the British fleet in Alexandria. The British, for their part, utilised midget submarines to seriously damage the fearsome German battleship Tirpitz.

Whereas the Navy SEALs have a specific unit tasked with operating SDVs — the SEAL Delivery Vehicle Team — the SBS has only one dedicated squadron. Z Squadron specializes in underwater insertion and attack operations using the SDVs.

Before settling on the MK 11, Naval Special Warfare Command was experimenting with the Advanced SEAL Delivery System (ASDS). At 65 feet, the ASDS was larger than an SDV (usually at around 22 feet). SEALs would ride within the ASDS and utilise its breathing apparatus. The ASDS was cancelled in 2009 because the project overshot its budget and the prototype was lost in a fire.

The British government will pay $90 million for the three SWCS.

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It’s interesting to read the British government’s announcement. Previously, it wouldn’t be necessary to explain why the purchase would also benefit the U.S. But with the “special relationship” in question after the election of President Donald Trump, it appears important to highlight the mutual benefits:

“The Government of the United Kingdom (UK) has requested to buy three (3) SEAL Delivery Vehicles (SDV) MK 11 Shallow Water Combat Submersibles (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.

This proposed sale will support U.S. foreign policy and national security objectives of the United States by improving the security of a NATO ally which has been and continues to be, an important partner on critical foreign policy and defence issues.

The proposed sale of the SDV MK 11 SWCS will continue U.K.’s maritime partnership, interoperability and regional security capability.  The UK has a proven track record of successfully deploying a predecessor system.  The UK will have no difficulty absorbing this system into its armed forces.”