Below is a list of Waterproof Switch manufacturers from Harvard, Illinois. A waterproof switch is a device that can interrupt the flow of a circuit while operating in a wet environment. Waterproof switches are frequently binary that either close or open the circuit; that is, they are either on or off. Other switches have several “on” options that are designed to handle varying amounts of voltage or current, which alters the output of the attached device, mechanism, appliance or piece of equipment.