Breakwaters'99 presents state-of-the-art methods and technologies that are used in the structural and environmental monitoring of rubble mound breakwaters. Structural monitoring concerns the structural response and the mechanical properties of the structure and its foundation. Environmental monitoring concerns the external loading on the structure and the effect the structure has on the total environment. These papers were presented at Breakwaters'99: First International Symposium on Monitoring of Breakwaters held in Madison, Wisconsin, September 8-10, 1999, and they discuss actual experiences in the field of monitoring breakwaters.