A submersible transformer assembly including a housing for holding an electrical transformer and having an aperture in a top panel of said housing for receiving a photocell assembly, the photocell assembly including a photocell positioned above the housing and electrically coupled with a socket held within the aperture by a socket retainer mounted to the underside of the housing top panel below the aperture. A transparent photocell cover or lens is mounted on top of the housing in covering and sealing relationship with the photocell and the aperture. The transformer positioned within the housing is electrically governed by the photocell which switches power to the transformer on and off in response to changes in ambient light conditions.