The problem of determining the total (acousto-electric) efficiency of a plate-type broadband piezoelectric transducer, which is loaded into an aqueous medium, was considered. The problem was solved taking the mechanical and dielectric losses in the piezoelectric material and the mechanical loss in a matching-layer material into account. Analytical expressions that determine the efficiency of a transducer and radiated acoustic power with account for losses were obtained. Numerical studies determined the main trends in changes in the total efficiency of this type of transducer in a wide range of values of both the mechanical quality factors of the ceramic and layer materials and the dielectric loss tangent for the ceramic material. These data can be of interest when designing piezoelectric devices for different purposes.