A semiempirical theory of breaking-induced mean currents on a beach is developed here to study the combined effects of refraction and diffraction. With the omission of convective inertia and lateral turbulent diffusion the resulting averaged equations are solved by finite differences. The case of an offshore breakwater is studied in detail, and the predicted current pattern is consistent with laboratory observations and the known tendency of tombolo formation near sandy beaches. Numerical results for an isolated breakwater extending from the shore are also presented, and observational evidences cited.