  We examine two means by which wind can impart energy to waves: sheltering and
deposition of material upwards from windward surface shear. The shear driven
deposition is shown to be the more efficient process. Lengthening of waves to
match the wind speed is shown to be very inefficient and consume a large
fraction of the energy imparted by the wind. The surface shear provides a low
energy sink that absorbs most of the momentum from the wind. These produce
bounds on the efficiency of wave growth. The results here are computed in a
model independent and perturbation free fashion by a careful consideration of
conservation laws. By combining these effects we can place bounds on the rates
waves can grow in a given fetch and the relative amount of shear flow versus
the, relatively small, Stokes drift that must arise.
