A hand-held water activated strobe light which may be used in rescue or emergency operations in peacetime or in a combat zone. The light includes a watertight housing with a high intensity bulb which flashes white light. Interchangeable blue and infrared filters attached to a flash guard body can be used with the bulb for filtering various wave lengths of light spectrum in combat situations and for both 360 degree or line-of-sight transmission. The strobe light is water activated and includes a sensor that deactivates the light during daylight hours. A memory latch circuit maintains activation of the light once the water activated switch comes in contact with water. A power saving circuit permits the use of alkaline batteries in place of mercury batteries, which also provides for environmental protection.