A multiple-detector irradiance meter and electronic depth-sensing unit for use in biological oceanography
The underwater irradiance meter or submarine photometer described here is designed to operate in the upper 100 to 150 m. It permits direct measurement of the downward blue-green irradiance (480 mµ) to a depth of 100-120 m on a clear day in water with an attenuation coefficient in the blue-green region of the spectrum of approximately 0.04/m. The meter can accommodate as many as five individual detector units as well as an associated depth-sensing element....
Holmes, Robert W., and James M. Snodgrass. 1961. "A multiple-detector irradiance meter and electronic depth-sensing unit for use in biological oceanography." Journal of Marine Research 19, (1). https://elischolar.library.yale.edu/journal_of_marine_research/963