  Using the KAM method, we exhibit some solutions of a finite-dimensional
approximation of the Zakharov Hamiltonian formulation of gravity water waves,
which are spatially periodic, quasi-periodic in time, and not permanent form
travelling waves. For this Hamiltonian, which is the total energy of the waves,
the canonical variables are some complex quantities an and a*n, which are
linear combinations of the Fourier components of the free surface elevation and
the velocity potential evaluated at the surface. We expose the method for the
case of a system with a finite number of degrees of freedom, the Zufiria model,
with only 3 modes interacting.
