The light sensitive strobelight starts flashing at sunset, enabling you and others to see your Kontiki at night. The strobe comes as a complete unit, being the base and the blub.
Most strobelights fail due to water getting into them because the top has been left loosen, either when the Kontiki is being washed or when it is launched into the surf.
The strobelight can be removed from the Kontiki body by using a flathead screwdriver. Screw the blub on, place the screwdriver under the lip of the base, and leverage the base out of the body while pulling the strobe out of the body.