The US State Department has approved the sale of three SEAL Delivery Vehicles to the UK.

The three MK 11 Shallow Water Combat Submersibles (SWCS) are to be purchased for an estimated cost of $90 million.

The system is a manned submersible, a type of swimmer delivery vehicle, and is currently used by the US to deliver United States Navy SEALs and their equipment for special operations missions. It is also operated by the Special Boat Service, which operates 3 SDV’s which the new systems are replacing. They’re used primarily for covert or clandestine missions to denied access areas (either held by hostile forces or where military activity would draw notice and objection).

It is generally deployed from the dry deck shelter on a specially-modified submarine, although it can also be launched from surface ships. The system fits inside the CHALFONT dry deck shelter on the Astute class submarines (pictured above), used to deploy special forces.

US Navy SEALs next generation SDV Mk.XI (SWCS)
Image of how the system will look, via HISutton.

The Defense Security Cooperation Agency delivered the required certification notifying Congress of this possible sale on September the 19th, 2018. This is displayed below:

“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.  The total estimated program cost is $90 million.

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 defense issues.

The proposed sale of the SDV MK 11 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.”

Image result for astute special forces
A US Navy SEAL pilots an earlier model MK8 Mod 1 minisub out of a dry dock shelter fitted atop a US Navy submarine.

The notice also adds that the prime contractor will be Teledyne Brown Engineering Inc in Alabama.

The Shallow Water Combat Submersible (SWCS) is a programme to replace the ageing SDV M.VIII Mod-1 SEAL Delivery Vehicle in use by both the US and UK.



  1. The documentation for this is over on Gabriel’s blog.

    A rare look at what some of the supposed 2 billion uplift in spending on UKSF, highlighted in the 2015 SDSR, is going on.

    Pictures exist of these SDV being used by the SBS down at Gibraltar, including air delivery by 7 Squadron Chinooks.

    Maybe they can lay Helions cables while they’re at it.

  2. The Astute class Chalfont shelters were built with the replacement SF submersibles in mind. The USN submarines had to extend their shelters to accommodate the new versions of these underwater vehicles.

  3. In the good old days we had fleet nuclear powered attack submarines SSNs for surface and subsurface warfare and the SSK fleet of diesel electrics for training crew on periscope course, NATO exercises as the threat vessels and for special forces insertion and operations.
    These new subs are a poor replacement for the SSK fleet

  4. Hang on 7 Astutes, at best 3 on patrol and we need 3 of these?, ridiculous.
    Surely we can do a share with the Seals and buy one and have an asset share. Crazy what are they Thinking? one on patrol, one on ops, one on refit. These are not Nukes, Just pressure vessels with a battery propulsion system they are not rocket science..more waste.

    • 1 for ops.
      1 spare in case the deployed one goes wrong.
      1 for training at the Chalfont training facility at Faslane or in reserve at Poole.

      Seems correct number to me.

  5. Is the SBS still large enough to require 3? The training sub can still do real ops. Not as if the Astutes would deploy 100% of time with these shackled on and SBS onboard, Just in case. Have to move on from buy 3 deploy 1. An Astute with the CSG, An Astute on anti sub patrols and another babysitting the deterrent. Leaves no sub for this. 2 max required.
    Fat chance there would be enough Astute to cater for this excellent kit.
    More chance the far more complex Astute goes wrong.
    Save some money buy 2 and give the Tides permanent sea sparrow or phalanx.

    • All good points, especially with the lack of SSNs. These should really be with some SSK saving our precious Astutes shouldn’t they.

      Can an Astute carry two Chalfont chambers if necessary? Incase more than one SDV was required for the mission? I’ve no idea?

      The only other suggestion I have is that apart from use by the SBS in MCT or raids one of these SDV may be for use by the Secret Intelligence Service. They have small, highly selective parts of the military in support, including a small section of the SBS who would no doubt operate the SDV on their behalf as SIS officers would probably lack that sort of skill set.

    • UK doctrine has not deployed an SSN with a CV for nigh on 50 years, they will not do so now for the QE class. RN does not subscribe to US CV BG doctrine. They do not have enough Boats for it.
      UK SN does not babysit the SSBN force. When a ‘Bomber’ goes to sea only a handful of people know where it is.
      UK SSNs are used primarily for ASW, with a secondary ASuW and land strike role (the latter of which has been most-used in recent years through force of circumstances).

  6. The issue with SSK’s is what would we really use then for? The RN wanted to go all SSN as soon as it had SSN’s and only accepted Upholder Class SSK as it felt it could not produce enough SSN’s to counter the soviet threat. SSN had some merit in helping us hold the GIUK line.

    However what would we really use them for today?

    SSN’s are the ultimate naval weapon and the single greatest non nuclear strategic weapon.

    The UK should invest and bring Astute production up to one per year and plan to copy the USA by continuing to build astute through out the production period of Dreadnaught class. That’s an affordable proposition for the UK that would substantially increase the UK’s military standing giving in the ability to stand up to even a country as powerful as China. SSN’s are incredibly difficult to build, we have perhaps the greatest SSN in the world in the Astute class, it’s madness to only have 6 when we could easily afford a fleet of 24.

    • We don’t have the indigenous infrastructure to build the Dreadnought-class and Astute-class at the same time without massively delaying the completion of the SSBN project.

  7. SSK’s are great for Defence of a coast line or choke point but it’s a Mission we have never performed even during the Second World War, we are always on the offensive and SSK’s have a limited use in offensive blue water operations.

    In addition all the roles an SSK can perform will soon be better performed by large UUV’s. We could buy and operate 10 of these for every SSK.


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