information:classification
Moored contact mines

Generally, this type of mine is set to float just below the surface of the water or as deep as five meters. A steel cable connecting the mine to an anchor on the seabed prevents it from drifting away. The explosive and detonating mechanism is contained in a buoyant metal or plastic shell. The depth below the surface at which the mine floats can be set so that only deep draft vessels such as aircraft carriers, battleships or large cargo ships are at risk, saving the mine from being used on a less valuable target. In littoral waters it is important to ensure that the mine does not become visible when the sea level falls at low tide, so the cable length is adjusted to take account of tides. During WWII there were mines that could be moored in 300 m (980 ft) -deep water.

Floating mines typically have a mass of around 200 kg (440 lb), including 80 kg (180 lb) of explosives e.g. TNT, minol or amatol.