Horizontal mean currents can transfer energy to or from internal waves as the waves propagate across the shelf and can also cause caustics that reflect the waves back across the shelf.The bar tropic flow is assumed to be weakly sheared, so that the effective change in the local rate of rotation caused by the mean flow relative vortices does not appreciably alter the dispersion relation for the intrinsic frequency of the wave.2. Whole-field kinematics measurements are presented of steep, steady waves travelling on strongly sheared currents, concentrating on the region between trough and crest level. For slab currents, the crest kinematics and wave parameters had found to be correctly obtained by using Doppler shifting and standard wave theories. When the current was sheared, the crest kinematics had found to be well predicted by adding the results of an irrotational model to the stretched current profile.3. The mean mass transport induced by surface gravity waves is investigated theoretically for a deep, rotating ocean with a constant eddy viscosity. The waves are periodic in time and have amplitudes that grow or decay slowly in space. The analysis is based on a Lagrangian description of motion, and the results are valid to second order in the wave steepness. An equation for the wave-induced mean Lagrangian mass transport in the oceanic surface layer is derived.