Submerged breakwater is a barrier with its crest at or slightly below the still water level. In situations where complete protection from waves is not required, submerged breakwaters offer a potentially economic solution. Submerged breakwaters have been effectively used to protect harbour entrances, to reduce siltation in entrance channels, against beach erosion, and for creation of artifical fishing grounds. However quantitative information available about the hydraulic behaviour of these submerged breakwaters is rather limited. Theoretical analysis of the problem has not proved satisfactory primarily because of the difficulties in quantifying the energy losses that always accompany these wave - structure interactions. Recourse has to be taken to laboratory studies to provide the necessary information regarding the performance characteristics of submerged breakwaters. A comprehensive laboratory investigation to evaluate the performance characteristics of the submerged breakwaters of various types and shapes, permeable and impermeable was undertaken. The results of these investigations are presented in this paper.