Schnorchel

During World War II the Germans experimented with the idea of the schnorchel (snorkel) from captured Dutch submarines, but didn't see the need for them until rather late in the war.

Finally, Allied radar eventually became sufficiently advanced that the schnorchel mast could be detected beyond visual range.

Sensors Radar detector The FuMB Ant 3 Bali radar detector and antenna was located on top of the Schnorchel head.

The schnorchel also had the effect of making the boat essentially noisy and deaf in sonar terms.

The Schnorchel (snorkel) and Type XXI boats appeared late in the war because of Dönitz's personal indifference, at times even hostility, to new technology he perceived as disruptive to the production process. von der Porten, op. cit.