Series of experiments are canied out to study the effect of breakwater side slope, bed slope and wave properties on the efficiency of submerged breakwater. Different equations were compared with the experimental results to adjust its validation with this phenomenon on sloping beaches. The summaries of conclusions are:1. The trapezoidal submerged breakwater efficiency is studied experimentally for different model side slopes (0:1, 0.5:1, 1:1, 1.5:1, 2:1) and wave frequency (0.1- 2.18) when the beach slopes are 0%, 1 %, 1.5% and 2%, blD=0.50.2. The trapezoidal submerged breakwater is efficient to control the transmitted waves when the relative breakwater height is greater than 0.75 and the beach slope is more steep3. The effective submerged breakwater side slope is 1.5: I and 2: 1 for horizontal and sloping beaches.4. The efficiency of submerged breakwater increases, for all beach slopes and breakwater side slopes, when the relative wave frequency decreases, 0)2h/g< 1.25.5. An imperical equation is suggested for the estimation of the transmission coefficient behind the trapezoidal submerged breakwaters.. The proposed numerical model gives a good estimation for the transmitted waves especially for veliical and nearly vertical breakwaters as well as the relative breakwater height decreases for different wave characteristics and beach slopes.7. The proposed numerical model was adjusted for the effective breakwater side slopes (1.5: 1 and 2: 1) by using a suitable calibration coefficient. The adjusted model gives a good estimation for wave characteristics when (02h/g>O.25.The summaries of recommendations are:1. Studying the efficiency of rubble mound submerged breakwaters constructed on movable sloping beaches.2. Studying the effect of the impermeable trapezoidal submerged breakwaters on the sediment transport and accordingly on the shoreline stability.3. Studying the effect of the breakwater crest width on the wave field around the impermeable trapezoidal submerged breakwaters.4. Studying the efficiency of the impermeable trapezoidal submerged breakwaters subject to oblique waves.5. Studying the efficiency of the impermeable trapezoidal submerged breakwaters under current-wave system.6. Studying the effect of the impermeable trapezoidal submerged breakwaters on the wave field when the breakwaters construct on movable bed.