Naval mine

A naval mine is a self-contained explosive weapon placed in water to damage or destroy surface ships or submarines. Similar to anti-personnel and other land mines, and unlike purpose-launched naval depth charges, they are deposited and left to wait until, depending on their fuzing, they are triggered by the approach of or contact with any vessel.

Naval mines can be used offensively, to hamper enemy shipping movements or lock vessels into a harbour; or defensively, to create "safe" zones protecting friendly sea lanes, harbours, and naval assets. Mines allow the minelaying force commander to concentrate warships or defensive assets in mine-free areas giving the adversary three choices: undertake a resource-intensive and time-consuming minesweeping effort, accept the casualties of challenging the minefield, or use the unmined waters where the greatest concentration of enemy firepower will be encountered.

Although international law requires signatory nations to declare mined areas, precise locations remain secret, and non-complying parties might not disclose minelaying. While mines threaten only those who choose to traverse waters that may be mined, the possibility of activating a mine is a powerful disincentive to shipping. In the absence of effective measures to limit each mine's lifespan, the hazard to shipping can remain long after the war in which the mines were laid is over. Unless detonated by a parallel time fuze at the end of their useful life, naval mines need to be found and dismantled after the end of hostilities; an often prolonged, costly, and hazardous task.

Modern mines containing high explosives detonated by complex electronic fuze mechanisms are much more effective than early gunpowder mines requiring physical ignition. Mines may be placed by aircraft, ships, submarines, or individual swimmers and boatmen.