Indicator net

They were intended to entangle U-boat traffic of the enemy, even though the submarines often managed to disentangle themselves and escape before being blown up by depth charges.

Predominantly deployed by the Royal Navy as a means of discouraging enemy submarines from entering Allied waters, indicator nets were used extensively during World War I.

Instead of being used as the sole anti-submarine measure, indicator nets were often mixed with extensive minefields and patrolling warships.

The first example of indicator nets causing the destruction of a U-boat occurred at Dover when the U-8 became entangled on March 4, 1915.

[3] The British continued to develop indicator nets between World Wars I and II, though the Americans did not.

Diagram showing the operation of an indicator net. The entanglement of the submarine causes a flare to automatically light on a buoy attached to the net, Office of Naval Intelligence (1917) [ 1 ]