KEY WEST, Fla. -- The U.S. Coast Guard discovered 7 tons of cocaine on a homemade submarine that featured sophisticated navigation equipment. Coast Guard officials said the apparent Colombian drug runners were taken by surprise on the 70-foot vessel. The sub was stuffed with $187 million worth of drugs. Four people were taken into custody in international waters. The vessel and the people aboard were on their way to Key West Thursday. The bust happened off the coast of Costa Rica after a U.S. Navy airplane spotted the sub.