Fluorescence may provide a rapid means of mapping the distribution of organisms on the sea floor, and perhaps in assessing their physiological condition. PSI has developed a variety of technologies for both imaging and spectral measurement of underwater fluorescence. These include filter sets that convert lights and camera systems for exciting and imaging fluorescence, and a self-contained diver-operated instrument for measuring fluorescence spectral emission without disturbing the specimen. These technologies are used in our own research efforts and some are made available commercially through NightSea, a PSI subsidiary.