Sieglinde (decoy)

Sieglinde was a decoy used during the Second World War by German U-boats. Similar to the Pillenwerfer noisemaker, except that it was powered by electric motors allowing to move at 6 knots (11 km/h) as well as rise and fall. The effect was that it sounded like a moving U-boat on Sonar. This allowed the real U-boat to slip away quietly from pursing ships. It was typically used in combination with Pillenwerfer noisemakers.