The purpose of the device, named "Ice Detector" is to sense the formation of ice on the surface of a body of water, and to place into operation whatever type of ice destruction system has been provided for that purpose. The principal benefit of the Ice Detector versus other means of turning on and off ice destruction systems is the protection of boats, docks, pilings and piers from damage from winter surface ice formation, while minimizing the wastage of electrical energy by operating ice destruction systems only when surface ice is actually forming. Other devices currently in use for this purpose, such as air thermostats, aquastats and timers, are ineffective to that end in that none of the variables monitored are directly related to the actual formation of ice on the water surface.