A naval mine is a self contained underwater explosive that when activated can destroy ships or submarines. The Confederates used naval mines as an effective defense against Union ships. To prevent the spread of the blockade, Confederates would place mines around a port to protect the waters from enemy attacks.
During the Civil War, mines took an innovative step into the future. Rather than being activated on contact, mines were invented such that they could be remotely detonated. Admiral David Farragut's famous statement, "Damn the torpedoes, full speed ahead!" refers to a minefield laid at Mobile, Alabama. During the Civil War, mines and torpedoes were often referred to as the same thing. Therefore, David Farragut said "Damn the torpedoes" even though he was referring to mines.