The design of water and wave retaining walls and flood risk analyses need hydrodynamic boundary conditions. These boundary conditions are needed during a storm with return period 1000yrs and during the super storms which were defined in the risk analysis study. The modelling of the extreme wave climate is decoupled to the wave penetration and the lacal generation of waves by the extreme wind speed. The wave penetration is modelled with Mike 21 BW as was done for Oostende and Zeebrugge. MILDwave is not used this time because non-linear effects (e.g. long wave generation, wave setup) are too important in this case. Instead another nonlinear model SWASH is applied. The modelling of local generation of waves by wind is still done with the spectral model SWAN. First the bathymetry files are created based on the dredging plan of Blankenberge marina, and all the suitable settings used for the Mike 21 BW and the SWASH are investigated. Since SWASH model does not have so much application examples, Wenduine physical model is used to validate the model. Consequently, a sensitivity analysis is conducted for both models to study which parameter is important for the wave climate inside the marina. The most severe offshore wave direction for the design of the wave retaining walls is decided based on the 1000 year storm. After the calculation of the wave penetration in the case of 1000 year storm and +7.9 mTAW storm, locally generated wind waves are also simulated by SWAN. All extreme wind speeds and directions for the 1000-year storm and the super storms are modelled. Finally, long and short wave energy of the wave penetration models is separated and a superposition of the short wave energy and the SWAN model is done to obtain the total extreme wave climate in the marina of Blankenberge. The maximum surface elevation of the long wave energy and the wave setup provide an increase of the still water level to take into account for design purpose.