U-480 Stealth Submarine (1943)
During WWII, the German Navy created the world's first stealth submarine, the U-480. A thin layer of rubber was added to it's skin to defeat the British sonar known as ASDIC. The sub went on 3 patrols, sinking 4 ships and shooting down an aircraft. In 1945 the sub was sunk and all hands were lost, except 1 who was left behind for training. During it's career, U-480 was never detected by Allied sonar.