Groynes are man-made structures built along riverbanks or beaches to prevent erosion and control the flow of water and sediment. These structures are also known as jetties, breakwaters, and revetments. Jetties extend out into the water and are designed to protect harbors and inlets from strong waves. Breakwaters are large structures built offshore to reduce the energy of incoming waves. Revetments are structures built along the bank of a river or beach to protect against erosion. All of these structures can be used interchangeably with groynes depending on their specific design and purpose. In summary, groynes are just one type of structure used for erosion control and water management, and there are several other synonyms that can be used to describe similar structures.