Construction of breakwaters in deep water involves various problems, such as the enormous mass of material which is needed. To solve this problem a new type of construction is proposed. It consists of floating prefabricated caissons towed to the site and fixed on piles. This type of construction which only partially cuts the port from the open sea does not act as a classie breakwater and the phenomenon characterising its behaviour is called « Fixed Water Wall ». In order to get a better understanding of this phenomenon, we have analysed it on a reduced model. Experimental and numerical study has been performed in the « MCcanique des Fluides et Genie Civil» Laboratory in Le Havre University. This study points out the mean effects of the phenomenon and the evolution of this system in an instantaneous way. It emphasizes the importance of the vertical velocities.
The advantages of this type of breakwater are obvious. It allows realisations in great depths as well as the construction of structures such as roads, buildings or car parks on it and also allows to build it in areas having few construction material resources. Numerous studies have already been done in an experimental way to analyse the feasibility of the projects and know the efficiency of the planned constructions. A theoretical study has been done by Bouchet and Manzane  to calculate transmission and reflection coefficients, taking the assumption of a potential flow. To get a good knowledge of this type of construction Bouygues Offshore Company, exclusive concessionaire of the patent (but the Principality of Monaco) concerns itself with the understanding of the phenomena that rule the « Fixed Waterwall» system and in this scope it entrusted the « Laboratoire de MCcanique des Fluides et Genie Civil» of Le Havre University with the task of studying the hydraulic functioning of this type of construction on a reduced model.