Since 2009 U.S. SOCOM (Special Operations Command) has been desperate to develop a small submersible vehicle to take SEAL commandos from a submarine or small ship to a hostile shore. The latest effort seeks to develop a SDV (SEAL Delivery Vehicles) using existing commercial submersibles. SOCOM also has to face the fact that there is not a big demand for an expensive, long-range SDV like the cancelled recently ASDS.
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 the last 60 years, efforts to design and deliver a workable replacement have failed.
The latest replacement candidate is the SWCS (Shallow Water Combat Submersible). This is a smaller version of the earlier ASDS (which was a cancelled 21 meter long, 60 ton mini-submarine.) Like the ASDS, the SWCS is battery powered, weighs ten tons or less 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.) The likely commercial minisubs to be converted to the SWCS have shorter range and won’t dive as deep as ASDS but, unlike ASDS, the SWCS is based on an existing design that works. Both navies want the SWCS, which will recycle some ASDS technology that worked, and replace the stuff that didn't.
There were a lot of Mk 9 replacements that did not make the grade. The latest was abandoned in 2009. This was the ASDS (Advanced Seal Delivery Systems) that was dropped after it discovered that 2008 fire damage would cost $237 million, and take three years, to repair. SOCOM was reluctant to repair the vessel and decided to just walk away. Originally, the entire program (including six ASDS) was to have cost $527 million, but it ended up costing nearly twice that to only produce 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.
The current plan is to have the SWCS in service by 2016. One can only hope.