Abstract: An underwater lighting fixture mounted in an aperture formed in the wall of a spa or other reservoir of water. An open-ended outer housing is disposed in a receiving aperture in the wall, and is secured thereto by a watertight coupling, the opening in the housing being directed to the interior of the enclosure. A light bulb and the electrical connections are mounted within the housing, the interior cavity of the housing being cylindrical and having screwthreads disposed about the inner circumference of the housing. The lens of the lighting fixture is integral with an inner cylindrical housing having screwthreads disposed about the outer circumference thereof and being adapted to engage the receiving screwthreads disposed on the interior surface of the outer housing. The inner housing is rotatably secured by engaging the screwthreads thereby forming a watertight seal therebetween.