Severe storms have gained more attention in recent years. Improved metocean data have lead to new insight into severer wave conditions for marine design. Therefore, there exists an industrial demand for fast and accurate numerical tools to estimate the hydrodynamic loads during e.g. green water events. In the WAVELAND and Wave Impact Load JIPs lead by MARINTEK, engineering tools were developed and a number of model tests were performed. KINEMA2 is one of these tools, which based on nonlinear random wave modeling combined with 3D linear diffraction theory to initially identify green water events, and then finally applied in simplified water-on-deck and slamming load estimation. This forms the background for the work presented in the present paper. Here we describe a new technique based on the use of Smoothed Particle Hydrodynamics (SPH), which can give more detailed forecast of the hydrodynamics on the deck. It uses a Lagrangian frame work (particles) to describe the fluid dynamics. The water propagation and kinematics of the green water events on deck are reproduced by using a SPH inlet condition where particles are injected with unsteady velocity from a rectangular plate against the deck and the deckhouse according to relative wave height and water particle velocities found from KINEMA2. These numerical results are compared against model test time series and previous results from other numerical simulation methods. This way the Lagrangian nature of this method (compared to traditional Eulerian-VOF methods) significantly reduces the CPU demand and increases the simulation speed. Slamming pressures can then be calculated e.g. from simple slamming formula calculations. In principle, pressures can also be found directly from the SPH calculations, while this would demand a significantly larger number of particle which increases CPU demand of the SPH method.