Measurements of the point spread function (PSF) were made in the Sargasso Sea in December, 1989. The water column during this period was extremely homogeneous therefore this data set became an obvious candidate to test the theories of Wells. This paper describes the results of this study. It's shown that the formalism (hence the implicit small angle approximation) works reasonably well for this case, with an average difference of 12% between the measured and predicted PSFs.
Kenneth John Voss,
"Variation of the point spread function in the Sargasso Sea", Proc. SPIE 1537, Underwater Imaging, Photography, and Visibility, (1 December 1991); doi: 10.1117/12.48874; https://doi.org/10.1117/12.48874