<p>Submerged breakwaters are widely used for coastal protection due to their relatively lower environmental impact compared with emerged structures; however, their hydrodynamic performance strongly depends on their geometric configuration. The present study investigates the hydrodynamic performance of porous submerged breakwaters with two geometric configurations: a tandem trapezoidal arrangement and a multi-slope profile. The analysis is carried out using the boundary element method (BEM) based on linear wave theory for water of finite depth. The hydrodynamic behaviour of the breakwaters is evaluated using wave-structure interaction parameters, including the reflection coefficient, transmission coefficient, and energy dissipation coefficient, which describe the proportions of incident wave energy reflected, transmitted, and dissipated by the structure. In addition, wave-induced horizontal forces acting on individual structural components are examined. In the case of the multi-slope configuration, the influence of geometric parameters such as the relative height of the stepped segments and the bottom width on wave attenuation characteristics is analyzed. Further, for the tandem configuration, the effects of the front and rear breakwater heights, as well as the spacing between the two units, are investigated. A detailed convergence study is conducted to ensure numerical accuracy, and the numerical model is validated through comparison with results available in the existing literature. The results indicate that both configurations are effective in attenuating wave energy, while the tandem porous breakwater provides greater flexibility in controlling wave transmission and dissipation through appropriate selection of spacing and breakwater heights. The findings provide useful design insights for optimizing porous submerged breakwaters and contribute to an improved understanding of wave attenuation mechanisms in complex submerged breakwater configurations for coastal and harbour protection.</p>