A narco-submarine (also called a drug sub or narco-sub) is a type of custom ocean-going, self-propelled, semi-submersible or fully-submersible vessel built by (or for) drug smugglers.[2][3][4]
Newer semi-submersibles are "nearly-fully" submersible in order to reduce likelihood of detection by visual, radar, sonar, or infrared systems.[3] Cargo capacity varies widely with vessel size, although several tons is typical. In 2015, the largest-known cargo of 7.7 tonnes (17,000 lb) was seized on a semi-submersible craft.[5] Some contemporary narco-subs are capable of crossing the Atlantic Ocean.[6]