The U.S submarine community's effort to foster a major increase in attack submarine (SSN) numbers is based primarily on the intelligence, surveillance, and reconnaissance (ISR) role. A traditional component of ISR activities has been the clandestine landing of people in foreign territory and their retrieval.
Until now, submarines had sent people ashore, primarily SEALs and other special operations forces, in rubber boats and in "wet" SEAL delivery vehicles (SDV). There are about 15 Mk VIII Mod 1 fiberglass vehicles in the fleet today, and each can carry eight SEALs using individual self-contained breathing apparatus, one of whom pilots the vehicle. The SEALs are wet and exposed to ambient temperature and pressure, as are their weapons and other equipment.
Trials now are being conducted out of Pearl Harbor of the long-awaited advanced SEAL delivery system (ASDS), a "minisubmarine" that will carry swimmers in a submarine-like environment. The craft—the first of six planned—is scheduled to become operational next year.