The MK VIII MOD 1 SEAL Delivery Vehicle is a free-flooding wet submersible designed for undersea special operations including direct action, hydrographic reconnaissance and insertion/extraction of SEALs. SDVs can be inserted into the water via a DDS-equipped submarine, MK V SOC or surface ships.
SDVs carry a pilot, co-pilot, and combat swimmer team and their equipment to and from maritime mission objectives on land or at sea. The pilot and co-pilot are often a part of the fighting team. The SDV has compressed air to extend the range of a swimmer's own air tank or rebreather. The SDV is lithium-ion battery powered and equipped with propulsion, navigation, communication, and life-support equipment.
The Mk VIII Mod 1 SDV can deliver several fully equipped SEALs to the mission area, be "parked" or loiter in the area, retrieve the SEALs, and return home. SDVs are generally launched from a Dry Deck Shelter on the back of a submarine, or from amphibious carriers (surface craft) equipped to launch and recover the SDV. It can also be airdropped (unmanned) into an operational area from a C-130 Hercules.