The objective of ComCoast (Combined functions in coastal defence zones) is to investigate how a multifunctional wide sea defence zone might be created. Instead of just increasing the height and weight of the dike, solutions are searched in the wide sea defence zone landward. These is an number of technical solutions, one of them is increasing the dike strength in orde to resist the load of water flow upon the grass revetment during extreme storms and handling the incomming water. WP3 aims at developing new concepts or further study of existing concepts together with the market parties to increase the dike strength in order to resist wave overtopping. The new concepts need to be cost-effective and social and environmental acceptable. In this report the sollution based on a stilling/retention basin idea is described. Besidses the concept a theoretical phase approach, global plan for test phase, costs and planning are given.