On Deviations from Gaussian Statistics for Surface Gravity Waves
  Here we discuss some issues concerning the statistical properties of ocean surface waves. We show that, using the approach of weak turbulence theory, deviations from Gaussian statistics can be naturally included. In particular we discuss the role of bound and free modes for the determination of the statistical properties of the surface elevation. General formulas for skewness and kurtosis as a function of the spectral wave action density are here derived. 
M. Onorato, A. R. Osborne, M. Serio