The instantaneous height of the entire surface of a fluid executing high amplitude motion can be obtained by photographing light that has been forced to diffuse through the liquid. This technique has been applied to resolve solitons and observe the frequency and wave-number spectra of ripple turbulence. Higher order correlations and various models of turbulence can be probed with this method.
Wright, W.B., Budakian, R., Putterman, S.J., Diffusing Light Photography of Fully Developed Isotropic Ripple Turbulence, Physcial Review Letters, The American Physical Society, College Park, MD, Vol. 76, pp. 4528-4531, June 10, 1996.