The SDV, which has been in continuous service since 1983, 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 is generally deployed from the Dry Deck Shelter on a specially-modified attack or ballistic missile submarines, although it can also be launched from surface ships or land.

The vehicle was then copied by the British when they discovered the Italian operations and called it the "Sleeping Beauty" or Motorised Submersible Canoe.

It had a hull made from fiberglass and non-ferrous metals to hinder detection and was powered by a silver-zinc battery attached to an electric motor.

[13] SDVs carry a pilot, co-pilot, and four person combat swimmer team and their equipment to and from maritime mission objectives on land or at sea.

USS John Marshall demonstrated this capability during a multilateral exercise in the Mediterranean when it recovered and then launched another country's SDV.

[16] Another advantage of the Mark 8 Mod 1 over its predecessor is that it is built from aluminium instead of plastic reinforced fiberglass, making its hull sturdier and roomier.

[17] These torpedoes can travel up to 3 nautical miles (5.6 km) in a straight line,[4] carry a 330-pound (150 kg) warhead, and are capable of sinking ships as large as cruisers.

[18] In addition to torpedoes, the Mark 9 also carried limpet mines and satchel charges in a large cargo compartment aft of the pilot and co-pilot.

[5] The Mark 9 is designed to clandestinely approach enemy vessels while submerged, surface to fire torpedoes, and then escape unnoticed.

[18] It was also faster than the Mark 8, reaching speeds of 7–9 knots (13–17 km/h), owing to its twin screw propellers and high-performance silver-zinc batteries.

[5] Its speed and agility led operators to compare it to flying a fighter jet or driving a sports car.

[20] It has been invaluable at deploying SEAL teams in clandestine missions, as it has enabled them to land on shores inaccessible to a larger submarine with a degree of stealth greater than that offered by small surface craft, helicopters, or other means.

The SDV's short range, which is contingent on sea state, water temperature, payload, and other factors, sometimes hinders operations.

In one example, the Navy wanted to use an SDV to get a closer look at a Soviet ship anchored in a Cuban harbor 18 miles (29 km) upriver from the Caribbean Sea.

The SDV could not have made the round trip to the Soviet vessel from an American ship outside of Cuba's territorial waters, so the mission had to be called off.

[2] Several days before the beginning of the 2003 invasion of Iraq, two SDV teams were launched from Mark V Special Operations Craft in the Persian Gulf.

After swimming under the terminals and securing their Mark 8 Mod 1s, the SDV SEALs spent several hours taking pictures and surveying Iraqi activity on both platforms before returning to their boats.

[6] However, reliability improved with usage: LCDR Lowe later commanded SDV Team 2 in the 1990s and reported that his subs were ready more than 90 percent of the time.

Modifying a surface ship to launch and recover the SDV through an underwater door, like the Italian Navy had done for its human torpedoes in WWII, would have helped alleviate this problem.