There are a few ways that jetty prevent erosion. The first is by providing a physical barrier between the shoreline and the waves. This barrier can be made of concrete, stone, or anything else that will break up the energy of the waves and stop them from reaching the shore. The second way is by creating an artificial reef. This is usually done by sinking ships or using large rocks to create a break in the water's surface. The third way is by building up sand dunes. This helps to protect the land from being eroded by wind and rain.