Detailed soundings of temperature and humidity between the surface and 1000 ft in warm air moving over cooler water are studied to determine the vertical transfer of heat and water vapor due to turbulence. Under simplifying assumptions, values of the eddy diffusivity are determined from the data at several heights and distances from shore and under varying wind and stability conditions. A simple model, in which the eddy diffusivity increases linearly with height in the lowest meter or two and is independent of height at higher levels, is shown to be consistent with the observations.