This paper presents experimental data on changes in underwater radiance in zenith and nadir directions as a function of depth for both overcast and clear sunny lighting conditions at the surface. The equation developed by Preisendorfer (1957) to describe path radiance along any path is then used to predict observed changes, and predicted results are compared with the observed data.
Tyler, J. E.. 1960. "Observed and computed path radiance in the underwater light field." Journal of Marine Research 18, (3). https://elischolar.library.yale.edu/journal_of_marine_research/953