[en] An apparatus for illuminating an underwater environment in a nuclear environment is described comprising: at least one unit comprising: an arc lamp for emitting light; a base for mating with and for conducting electricity to said arc lamp; a seal for creating a watertight connection between said arc lamp and said base; a light-transmissive impact-resistant cover for enclosing said arc lamp, said base and said seal; and a releasable connector attached to said base; a polished reflector partially surrounding said at least one unit to control the direction of the reflection of light emitted from said arc lamp of said at least one unit; a cable means for providing electricity to said connector; and a ballast power supply contained in a watertight housing and connected to said cable means; wherein said unit is replaced by disconnecting said releasable connector from an old said unit and connecting it to a new said unit