Drug traffickers are spending $1 million a pop to build boats that look like submarines and can carry 4 tons of cocaine for 2,000 miles without refueling. Nicknamed "narco subs," they're made to sneak loads up from South America to Mexico, where the drugs are offloaded and taken overland into the United States. "It is a semi-submersible coffin," said Jay Bergman, Andean regional director for the Drug Enforcement Administration. "You batten down the hatches and you are doing everything to not be detected sailing in the middle of the ocean." At least 13 of the craft have been stopped and...