Once dismissed as a novelty, US officials are no longer laughing at drug cartels' use of submarines to transport cocaine. More than a third of the cocaine smuggled from Colombia is now believed to enter the country through submersibles, with drug cartels employing a crudely built armada of dozens of the vessels. Officials warn that the ships are becoming more advanced and that sub-builders are working on remote-controlled models that will be able to do the job without risking dealers' being arrested or killed. As it is, the subs can be difficult for anti-narcotic agents to spot. "You try finding a floating log in the middle of the Pacific," one DEA agent said.