There has been a significant interest in the last two decades in the use of vertical flexible structures as breakwaters. These structures provide an alternative to the conventional rigid-fixed breakwaters in areas where poor foundation conditions exist or where protection is required on a temporary basis. These kinds of structures can be quickly deployed, are reusable and can act as low cost wave protection systems compared to those of the rigid-fixed structures. The permeability characteristic of these structures will dramatically reduce the reflected and transmitted wave heights along with the hydrodynamic forces acting on the structures. These kinds of structures can be effectively used for oil spill containment, for temporary protection during coastal construction works, for augmentation of existing breakwaters and for seasonal protection (as in [73], [136] and [152]). Thus, accurate prediction of transmission characteristics and the dynamic response of these flexible porous breakwater are of significant importance in coastal-engineering practices.