For US, a terror threat lurks in drug smuggling subs Shift of cargo to arms and people is feared By Bryan Bender KEY WEST, Fla. - Skimming just below the surface, they are extremely difficult to detect from surveillance aircraft or patrol boats. Their sleek design, up to 80 feet in length, can secretly carry several tons of cargo thousands of miles. These "semi-submersibles," which exhibit some of the same characteristics as military submarines, mark a significant advancement in the ability of drug smugglers to slip past coastal defenses. So far this year, the Coast Guard says it has encountered...