<p>This study aspires to analyze a wave energy converter (WEC) through its hydrodynamic efficiency featuring a stationary submerged thin vertical plate (STVP) situated at free surface level (<i>z</i> = 0&#xa0;m). The investigation incorporates arrangements with both flat and uneven seabed profiles, and also various wave steepness conditions. To perform the computational work, a numerical wave tank (NWT) is developed utilizing the ANSYS Fluent 2024 R2 software, and the fluid interface tracking is done employing the volume of fluid (VOF) approach. Stokes waves of second-order are produced at NWT entrance using the inflow velocity approach, and the wave reflection is minimized at the end by using numerical damping. The effect of four distinct relative opening (<i>α</i>) and wave height (<i>H</i>), with uneven bottom, is evaluated and subsequently compared to the hydrodynamic efficiency over a flat sea bed. The study is conducted for four distinct wave time periods (<i>T</i>) in the range of 1.16–2&#xa0;s. The axial flow velocity under the stationary plate is computed for various conditions, such as (a) thin plate only, (b) thin plate and a trapezoidal structure of distinct altitude below it. This research study illustrates that optimal efficiency occurs at <i>α</i>_<i>2</i> = 50%. Additionally, axial flow velocity (<i>v</i>_<i>x</i>) exhibits elevated values at <i>T</i> = 1.87s for increased wave steepness. The findings indicate noticeably improved hydrodynamic efficiency with higher wave steepness.</p>