During this research a method is developed for finding the cost optimal design of a sea dike when a probabilistic method is being applied and flexibility is allowed in the distribution of the total failure probability over the various failure mechanisms. A probabilistic model has been set up to calculate the cost optimal design for a sea dike while taking into account the failure mechanisms overtopping, armour layer stability and macro-stability of the inner slope and a number of input geometries that differ in crest height, outer slope angle, berm dimensions and stone size of the armour layer. The model has been evaluated with a case study and the results have been subject of a sensitivity analysis. Based on this case study it is concluded that when using a probabilistic approach and introducing more flexibility in the distribution of the total failure probability over the various failure mechanisms, a cost saving design may be found. This is achieved by changing the key dimensions of the dike section in such a way that trade-off of failure space between the various failure mechanisms occurs.