Marine dye marker used for daytime emergency distress signalling and search and rescue marking. A person in distress scatters the dye marker on the water when a potential rescue vessel or aircraft appears. It spreads as a brilliant spotting mark. clearly visible as a distress signal for up to an hour. and in good visibility can be seen by aircraft over 10 km away. Ideal for boating. it is also an extra safety equipment for windsurfing. diving and snorkeling.