  The study is motivated by recent findings of the decrease in the momentum
transfer from strong winds to sea. The Kelvin-Helmholtz instability (KHI) of a
three-fluid system of air, foam and water is examined within the range of
intermediately short surface waves. The foam layer thickness necessary for
effective separation of the atmosphere and the ocean is estimated. Due to high
density contrasts in the three-fluid system, even a relatively thin foam layer
between the atmosphere and the ocean can provide a significant stabilization of
the water surface by the wavelength shift of the instability towards smaller
scales. It is conjectured that such stabilization qualitatively explains the
observed reduction of roughness and drag.
