Wind speeds have been measured elaborately over the shallow water (3cm depth) and also over the flat plate in a large wind wave tunnel with the use of a Pitot static tube. The waves formed thus are rather small (H1/3<1cm). It is checked for the cases over flat plate that a logarithmic law of wall actually holds good over from fifteen to twenty percents' lower portion of the boundary layer. The profiles over the water show not only a logarithmic distribution over the same region next to the surface, fut also a close resemblance to those over the plate with regard to the other behavior of the foundary layer.
　Assuming the logarithmic law is applicable over water, values of the surface shear stress τ0 and roughness parameter z0 are evaluated. The drag coefficient γ2 (=τ0/ρa U210) has a tendency to depend on the fetch to some extent. It becomes nearly independent of the wind velocity for the longer fetch and varys between 0.9×10-3. and 1.0×10-3 It may be inferred that the form drag is reduced considerably.