The interaction of wave overtopping and the soil properties of a seadike is responsible for the initiation of dike failures and the breaching process. Unfortunately, the present design of seadikes is based on the separate determination of hydraulic and geotechnical design parameters. Therefore, large scale hydraulic model tests were set-up on the basis of a detailed failure analysis for seadikes to investigate the infiltration and erosion process due to wave overtopping. Results are presented in this paper.