Abstract: A control module including circuitry therefor, which prevents short circuit conditions of a boat trailer's light-circuitry at the boat-launch site, in which at least two co-ordinated control circuits are provided to assure that none of the trailer circuits are energized while the trailer is in the water body of the lake or stream at the launch site. Both the circuits are provided as branches of the towing vehicle's own circuitry. One is provided to be a branch of the vehicle's backup lights' circuitry, utilizing the fact of the boat-launch and retrieval maneuver normally including a reverse-drive action of the towing vehicle, which assures energizing of that first control circuit.