Abstract This article outlines the minimum set of concepts of hydrological optics required for an understanding of solar energy penetration into bodies of water. The practical application of these concepts to solar ponds, especially by means of the Monte Carlo modeling procedure, is discussed, and an account is given of the optical measurements that need to be made in order to arrive at an understanding of radiation transfer within any given solar pond. The results are presented of a series of Monte Carlo calculations of the behavior of solar radiation within idealized but realistic solar ponds with optical properties covering a wide range of values. The effect on energy collection efficiency of varying the concentration of colored substances, the scattering coefficient, and the albedo of the bottom are explored in detail. The optical criteria that must be satisfied for successful solar pond operation are briefly discussed.