A naval mine configured to be released by a release assembly comprising: an impermeable casing; an explosive charge arranged inside the impermeable casing; a detonator which can be operated to trigger the explosive charge; and a control device configured to operate the detonator. The naval mine further comprises a fillable chamber, provided with at least one opening and a closing system for closing or opening the opening; said closing system is configured to open the opening so as to allow water to flow into the fillable chamber, when the naval mine is released by the release assembly.