The ACR SM-2 Automatic Marker Light (ACR# 3940.1). This strobe light is meant to be tossed into the water to mark a man-overboard site, and to illuminate the scene for rescue with each brilliant flash. The 70,000 peak candle power, high-intensity xenon strobe operates for up to 50 hours. Weighing just 31/4 pounds, it's waterproof, shock resistant (withstanding 90 foot air drops, no problem), and non-corrosive. Light is activated automatically when tilted upright or dropped in the water. Powered by a 6-volt lantern battery. USCG-approved SOLAS, float-free bracket (required for commercial vessels).