We applied canonical transformation to water wave equation
not only to remove cubic nonlinear terms but to simplify drastically fourth order terms in Hamiltonian for water waves equation. After the transformation well-known but cumbersome Zakharov equation is drastically simplifyed and can be written in X-space in compact way. This new equation is very suitable for analytic study as well as for numerical simulation. At the same time
one of the important issues concerning this system is the question of its integrability. The rest part of the work is devoted to numerical and analytical study of the integrability of the equation obtained. In the second part we present generalization of the improved Zakharov equation for the "almost" 2-D water waves at the surface of deep water. When considering waves slightly inhomogeneous in transverse direction, one can think in the spirit
of Kadomtsev-Petviashvili equation for Korteveg-de-Vries equation taking into account weak transverse diffraction. Equation can be written in terms of canonical normal variable b(x; y; t). This equation is very suitable for
robust numerical simulation. Due to specific structure of nonlinearity in the Hamiltonian the equation can be effectively solved on the computer. It was applied for simulation of sea surface waving including freak waves appearing