Abstract: Improved techniques are provided for opening or closing an underwater valve in a subsea fluid pipeline utilizing an acoustic signal transmitted from the surface to a receiver adjacent the valve. A predetermined torquing force is applied to a shaft directly coupled to the valve stem, although rotation of the valve stem is prevented by the mechanical connection of an explosive bolt. Receipt of the transmitted acoustic signal initiates the release of stored electrical energy which detonates the explosive bolt and breaks the mechanical connection, thereby enabling the pre-existing torquing force to rotate the valve stem. Valve operation reliability is significantly increased, since the torquing force for operating the valve is applied before the valve is installed in the subsea environment.