Type UC II minelaying submarines were used by the Imperial German Navy during World War I. They displaced 417 tons, carried guns, 7 torpedoes and up to 18 mines. The ships were double-hulled with improved range and seakeeping compared to the UC I type. If judged only by the numbers of enemy vessels destroyed, the UC II is the most successful submarine design in history: According to modern estimates, they sank more than 1800 enemy vessels.