  We develop a theory of turbulence of weak random gravity waves on surface of
deep water in which the main nonlinear process at high-frequency part of the
spectrum is a nonlocal interaction with a strong low-frequency component. The
latter component, which we call ``condensate", may appear in the system due to,
e.g., the finite size effects which lead to an energy stagnation at waves whose
wavelength is comparable to the size of the retaining flume. Our theory assumes
the form of a linear spectral diffusion equation. We find a scaling solution of
this equation and propose it as a possible explanation of recent numerical
results for the gravity wave spectrum.
