And the water just finds its way around the back of the rocks rendering the billion $ project a failure. In essense, the shorelines will continue to receed away from the rocks. fricking retarded engineering at its finest.
Not sure if trolling or serious....
On the off chance you're being serious:
The rock dikes act as a wave break to prevent further erosion. The energy contained in the waves is dissipated by the rocks. The water still passes through and over the rocks and eventually land will actually build up behind the rocks closing the gap. When the waves are dissipated, the slow moving water behind the rocks deposits sediment allowing for land building.
There is nothing retarded about it. It is a proven method of wave dissipation, erosion prevention and land building. I will pray for the people of this world that you are not an engineer and never took a physics class.