Back during World War II, the Office of Strategic Services (OSS) began working on their own version of an Italian invention that was essentially a motorized submersible canoe. While the Italians had been using a version since World War I with some success the OSS never got past developing and testing prototypes. The United States also experimented with one-man submersibles for Underwater Demolition Teams, but the idea never saw any practical application during the war.
Post-war, a small team at General Dynamics continued to develop Swimmer Delivery Vehicles (SDV) through the 1960s resulting in the MK7 variant seen in these pictures was tested from 1967-1972 before being deployed for the first time in 1968. The MK7 had a fiberglass hull, and nonferrous materials were used to minimize acoustic and magnetic signatures. It had an operating depth of 500 feet and its electric motor was powered by silver-zinc batteries.
The SDV name designation would swap Swimmer with SEAL making these SEAL Delivery Vehicles, and would see their first real test during the Vietnam War. The USS Grayback (LPSS 574) a submarine modified to carry up to four SDVs was put into theater in 1968 to support SEAL missions. In 1972, Operation Thunderhead would use an MK7 SDV in a rescue attempt of US prisoners of war.
By 1975 the MK7 Mod 6 variant was introduced that added additional weapons payload capacity, better sonar avoidance technology, and an emergency ballast tank blow. Shortly after the MK8 would become the primary SDV used by the Navy, it added an underwater radio system and a sliding canopy to reduce drag.
SDVs have been deployed during the First Gulf War, the Iraq War, and the 2003 Invasion of Iraq for surveillance of coastal defenses, off-shore oil and gas terminals, and naval assets. SDVs were also used to install covert surveillance cameras along the Somali coastline to monitor terrorist groups. A n updated version of the MK8 SDV is still in service to this day by the US Navy SEALs and the Royal Navy Special Boat Service.
Want your own SDV? A commercial version was offered as the Convair Model 14, with the hopes that oil companies would use them to transport divers to underwater worksites or use them to perform inspections on off-shore oil platforms. However, there is little to show that outside of a few prototypes that the Convair Model 14 was a commercial success.
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