SDV Teams - SEAL Delivery Vehicles (SDV) & Dry Dock Shelters (DDS) US navy divers are an important component of the Seal SDV teams. The Seals, already burdened with mission specific planning and preparation, depend on the navy divers for a variety of diving services including the launch and recovery of SDVs. By having navy divers on an operation to do what they do best, dive, the Seals are then free to concentrate on their mission knowing that they are in safe and competent hands. SDVT-2 for example has 28 navy divers in the command, in addition to Seals and SDV technicians. Qualified navy divers are trained at SDVT-2’s headquarters in Little Creek, taking about 6 months to learn all the SDV/DDS operations. When an SDV Team deploys, they deploy as a 30-man Task Unit package including 10 navy divers. There are thirteen manned stations associated with an SDV launch from a DDS, seven of those are wet requiring divers. Any U.S. submarine can carry SEALs, however the Navy has several submarines that have been specifically modified to carry swimmers and their equipment more effectively, including the installation of Dry Deck Shelters (DDSs) to house SEAL Delivery Vehicles (SDVs). The DDS can be used to transport and launch an SDV or to "lock out" combat swimmers. It can be installed in about 12 hours and is air-transportable, further increasing special operations flexibility. For most operations a large submarine would not want to go too shallow, so an SDV is necessary for the final approach to the beach or harbor facility. Coastal Systems Station was responsible for developing the Mk-VIII and Mk-IX boats and continues to be responsible for their maintenance. The DDS is 9 feet wide, 9 feet high, 38 feet long and consists of three interconnected compartments each capable of independent pressurization. The forward-most compartment, a sphere, is the hyperbaric chamber which is used for treatment of injured divers. In the middle compartment, or transfer trunk, operators enter and exit the submarine and/or either of the other compartments. The third compartment, the hangar, is a cylinder with elliptical ends which houses either the SDV or up to 20 SOF personnel with CRRCs. The DDS, fitted aft of the submarine's sail structure, is connected to the submarine's after hatch to permit free passage between the submarine and the DDS while the submarine is underwater and approaching the objective area. Then, with the submarine still submerged, the SEALs can exit the DDS and ascend to the surface, bringing with them equipment and rubber rafts, or they can mount an SDV and travel underwater several miles to their objective area. The dual DDS submarine has inherent redundancy compared to the single DDS since the DDSs operate and interface with the submarine systems totally independently. Therefore, a material casualty on one system would not result in aborting the mission. With an expected service life of at least 40 years, Dry Deck Shelters will likely continue to support the missions of Seal Delivery Vehicle deployment and Mass Swimmer Lock-Out, serving both the Special Operations Forces and submarine warfare specialties for many years to come.