The Colombian Navy intercepted a semi-submersible ship that was sailing to Central America with over three thousand kilograms of cannabis. The ship was intercepted early on Friday morning and three Colombian nationals were arrested. The Colombian navy said the seized cannabis is worth $21 million. However, the estimated value of busts is often based on consumer street value and is hence inflated compared to the bulk value of the cargo for traffickers.

The use of semi-submersible ships, or narco-subs as they’re often called, is a growing method of drug trafficking for Colombian smugglers. However, this seizure is a little unusual as the narco-subs are more often used to traffic the more lucrative cocaine. For example, earlier this month, Colombian authorities seized the largest ever narco-sub to date which held three tons of cocaine.

Narco-subs are nearly fully submersible which makes them hard to detect visually, and through sonar and radar systems for authorities. They first saw use for drug trafficking in the mid-1990s and have been growingly used since. Narco-subs primarily move cocaine out of Colombia to Central America before it reaches the final destination of the US consumer market.