It is not widely appreciated that mines were by far the most effective weapon deployedby Germany against the Royal Navy in WW1.
They cost Britain five battleships, three cruisers, twenty-two destroyers, four submarines and a host of other vessels.Mines were generally combated by a civilian force that sailed in a variety of commandeered vessels such as fishing boats and paddle steamers.
This unlikely armada saved the day for Britain and her allies.
After 1916 submarine attacks on merchant ships became an even more serious threat to Allied communications but enemy submarines were far less damaging to British warships than mines.
Whereas in 1914 the Admiralty rather scoffed at mine laying as a sneaky un-British form of sea warfare, by the later stages of the war the Royal Navy learnt to use mines as a primary anti U boat weapon, developing an amazing variety of mined obsticles and mine laying vessels.