A general description of a phosphorescent bay on the northern shore of Jamaica, West Indies, is presented. The brilliant bioluminescence in this embayment is due to the large armored dinoflagellate, Pyrodinium bahamense. It was found in cell densities as high as 200,000 cells/liter. Using a submersible spectrometer, the bioluminescent emission spectrum of these organisms was found to peak at 476 mµ....