Aircraft from Felixstowe repeatedly swept the Spider's Web patrol pattern near the Thames and Channel barriers and the Strait of Dover. A submarine trying to pass had to risk surface detection or remain submerged, spending battery power, fuel, food, water, and patrol time. Aircraft could also summon surface ships once a boat was seen, turning an attempted transit into a wider hunt. The pattern therefore made aviation both a search system and a barrier: it prevented an ambush predator from reaching a useful position even when no kill followed.
Chapter · 23:46-26:12
The Spider's Web flying-boat patrol
Examine the Spider's Web search pattern that constrained submarine transit through the Channel approaches.