A narco-submarine (also called a drug sub or narco sub) is a type of custom ocean-going self-propelled typically semi-submersible (sometimes fully-submersible) vessel built for smugglers. Newer submarines are 'nearly-fully' submersible to be difficult to detect visually, by radar, sonar, or infrared systems. Cargos are typically several tons. In 2015, the largest-known cargo of 7.7 tonnes (17,000 lb) was seized on a semi-submersible. The capabilities of these craft are increasing (some are capable of crossing the Atlantic Ocean); their operating places and circles are widening; and their numbers are growing. The drug trafficker Laureano Oubiña affirms the existence of a marine cemetery of narco-submarines near the Canary Islands (Spain). From Wikipedia