  Some data of the drift current, Ud, measured on a wavy surface of water in a
laboratory and the field, are briefly described. Empirical formulas for Ud are
given, and their incompleteness is noted, regarding to absence of the drift
current dependence on surface-wave parameters. With the purpose of theoretical
justification of empirical formulas, a semi-phenomenological model of the
phenomenon is constructed. It is basing on the known theoretical and empirical
data about the three-layer structure of the air-water interface: 1) the air
boundary layer, 2) the wave-zone, and 3) the water upper layer. It is shown
that a presence of linear drift-current profile in the wave-zone, U(z), makes
it possible to obtain a general formula for the drift current on the wavy water
surface, Ud. This model is based on the balance equation for the momentum-flux
and current-gradient, taking place in the wave-zone. The proposed approach
allows us to give an interpretation of the empirical results, and indicate the
direction of their further detailed specification.
