In the reliability-risk assessment, the second order reliability index method and the Conditional Expectation Monte Carlo (CEMC) simulation were interrelated as a new Level III computational approach in order to analyse the safety level of the vertical wall breakwaters. The failure probabilities of sliding and overturning failure modes of the Minikin method for breaking wave forces were forecasted by approximating the failure surface with a second-degree polynomial having an equal curvature at the design point. In this new computational approach, for each randomly generated load and tide combination, the joint failure probability reflected both the occurrence probability of loading condition and the structural failure risk at the limit state. This new approach can be applied for the risk assessment of vertical wall breakwaters in short CPU durations of portable computers. © Springer-Verlag Berlin Heidelberg 2005.