Abstract: A diver's flashlight having a unitary case with a closed transparent end for light transmission, the other end being sealed by a threaded plug which also serves as a switch. A halogen bulb is mounted in a reflector immediately inside the transparent end and a rechargable battery is held normally out of contact with the bulb by a spring. Tightening the threaded plug overcomes the spring and completes the circuit when the plug is fully seated in sealed position. The plug, and a cap fitted over the transparent end, are of luminous material for night use.