For decades U.S. SOCOM (Special Operations Command) has been trying to develop a new SDV (SEAL Delivery Vehicles). These are small submersible vehicles to take SEAL commandos from a submarine or small ship to a hostile shore. SOCOM has finally placed an order for a militarized version of the S302 commercial submarine. This 27 ton vessel is called a DCS (Dry Combat Submersible) SDV. There is already a “wet” SDV but a DCS version has been long sought because it delivers SEALs to a hostile shore in better shape physically and psychologically to handle their mission on land. SOCOM has ordered three of these DSCs for $55.4 million each. Each DSC can carry a crew of two and six SEALs and their equipment. Max depth is 100 meters (320 feet) and max speed is nine kilometers an hour. Other specifications were not released but based on S302 capabilities the DSC will be carried on the deck of a nuclear submarine and can be entered from inside the sub and then released up to a hundred kilometers from shore and get the SEALs to land within ten hours.
In the meantime the Mk 8 SDV, which is a World War II era design that is basically a reusable torpedo which divers in scuba gear hang on to as they are taken to shore, is still all that is available. The MK 8 has long been used by American and British combat swimmers. Both nations are still using the MK 8 and despite all the new tech developed in since World War II ended in 1945, efforts to design and deliver a workable replacement have failed so far. There were a lot of Mk 8 replacements that did not make the grade, all of them designed as military, not commercial, submersibles.
The most recent attempt for a purely military DCS was the ASDS (Advanced Seal Delivery Systems) which was abandoned in 2009 after it was discovered that fire damage suffered in 2008 to the only one built would cost $237 million, and take three years, to repair. SOCOM was reluctant to repair the vessel and decided to just walk away from the 21 meter long, 60 ton mini-submarine. Originally, the entire program (including six ASDS) was to have cost $527 million, but it ended up costing nearly twice that to only produced one. While a nice piece of engineering, each ASDS would have cost over $300 million. The U.S. Navy also spent $47 million building a base in Hawaii for the ASDS fleet. There, and in the Persian Gulf, the first ASDS production boat underwent testing for three years, before being declared ready for service in 2004. But problems kept cropping up, until the production of the other five was cancelled in 2006. After a decade of development, the ASDS had too many technical problems. Only the first one remained and it sort of worked until it caught fire.
Until 2015 there was still a military developed candidate; the SWCS (Shallow Water Combat Submersible). This was a smaller version of the earlier ASDS. Like the ASDS, the SWCS is battery powered, with a crew of two and carries about six SEALs. The larger ASDS could carry up to 14 passengers (fewer if a lot of equipment is being brought along, the usual number of passengers was expected to be eight.) With a max range of 200 kilometers, top speed of 14 kilometers an hour and max diving depth of 65 meters (200 feet), the ASDS was to operate from one of the seven U.S. nuclear submarines and several British boats equipped to carry it on the deck. Both ASDS and SWCS are equipped with passive and active SONAR, radar and an electronic periscope (that uses a video camera, not the traditional optics.)
In the end it was decided to find an existing mini-sub model that was cheaper and known to work. In 2015 it was hoped that SWCS would prove suitable but it wasn’t and now one of several suitable, serviceable civilian mini-sub models became the long sought DSC SDV.