SEAL Delivery Vehicle

The SEAL Delivery Vehicle or (SDV) is a manned submersible and a type of Swimmer Delivery Vehicle or diver propulsion vehicle used to deliver United States Navy SEALs and their equipment for special operations missions and is also operated by the Royal Navy's Special Boat Service who operates 3 SDV's.

The SDV is 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 should not be confused with the larger, dry submersible called the Advanced SEAL Delivery System (ASDS). The SDV is flooded, and the swimmers ride exposed to the water, breathing from the vehicle's compressed air supply or using their own SCUBA gear. (The ASDS is dry inside, with a full life support and air conditioning system.)

The SDV program dates back to World War II. Initiated by the Office of Strategic Services Maritime Unit (OSS MU). A “submersible canoe” was invented by the Italians during World War I . The idea was successfully applied by the Italian navy (Regia Marina) also early in World War II. The official Italian name for their craft was Siluro a Lenta Corsa (SLC or "Slow-running torpedo"). The vehicle was then copied by the British when they discovered the Italian operations and called it the “Sleeping Beauty”. It was employed by OSS MU during extensive training and exercises, but was never actually deployed for combat operations. The same capability was adopted by the post-war Underwater Demolition Teams (UDTs) in 1947. The one-man submersible displayed little functional military potential; however, it substantiated and characterized the need for improved and expanded UDT capabilities. After the war, development continued in a garage-shop fashion by various UDT units, and included various "Marks" as the MK V, VI, VII, and XII. Intermediate numbers were assigned to some vehicles that never made it off the shop floor. All were of flooded design.

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