was the . was another such minelaying submarine. Although there are no modern submarine minelayers, mines sized to be deployed from a submarine's torpedo tubes, such as the Stonefish, allow any submarine to be a minelayer. In modern times, few navies worldwide still possess minelaying vessels. The United States Navy, for example, uses aircraft to lay sea mines instead. Mines themselves have evolved from purely passive to active; for example the US CAPTOR (enCAPsulated TORpedo) that sits as a mine until detecting a target, then launches a torpedo. A few navies still have dedicated minelayers in commission, including those of South Korea, Poland, Sweden and Finland; countries with long, shallow coastlines where sea mines are most effective. Other navies have plans to create improvised minelayers in times of war, for example by rolling sea-mines into the sea from the vehicle deck through the open aft doors of a Roll-on/roll-off ferry. In 1984, the Libyan Navy was suspected of having mined the Red Sea a few nautical miles south of the Suez Canal using the Ro-Ro ferry Ghat, other nations suspected of having similar wartime plans include Iran and North Korea. Aerial minelaying Beginning in World War II, military aircraft were used to deliver naval mines by dropping them, attached to a parachute. Germany, Britain and the United States made significant use of aerial minelaying. A new type of magnetic mine dropped by a German aircraft in a campaign of mining the Thames Estuary in 1939 landed in a mudflat, where disposal experts determined how it worked, which allowed Britain to fashion appropriate mine countermeasures. The British Royal Air Force minelaying operations were codenamed "Gardening". As well as mining the North Sea and approaches to German ports, mines were laid in the Danube River near Belgrade, Yugoslavia, starting on 8 April 1944, to block the shipments of petroleum products from the refineries at Ploiești, Romania. "Gardening" operations by the RAF were also sometimes used to assist in code breaking activities at Bletchley Park. Mines would be laid, at Bletchley Park's request, in specific locations. Resulting German radio transmissions were then monitored for clues which could help deciphering messages encoded by the Germans using Enigma machines. In the Pacific, the US dropped thousands of mines in Japanese home waters, contributing to that country's defeat. Aerial mining was also used in the Korean and Vietnam Wars. In Vietnam, rivers and coastal waters were