The main failure of the SDV is its poor mobility. The SDV can only be effectively deployed from specially modified submarines and surface ships. Although it can be transported by C-130 airplanes, the relative scarcity of vessels capable of deploying an SDV limits its usage. Submarines are the preferred means of deployment, as enemies can see a surface ship deploying an SDV with a crane, further limiting the SDV's mobility and usage. 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.