This study presents an innovative design for a wave energy converter (WEC). The system is based on a novel mechanical power take-off (PTO) device that can absorb wave energy by converting the bidirectional motion of an ocean wave into the one-way rotation of an electric generator. First, the PTO mechanism and configuration are described in detail. A coupled mechanical and hydrodynamic time-domain simulation of a hemispherical floating buoy connected to a bidirectional gearbox and torque generation device under regular waves were modelled in MATLAB®/Simulink®. The hydrodynamic forces acting on the semi-submerged floating buoy are calculated by employing linear potential wave theory. The friction behaviour in the PTO system is modelled by using Brian Armstrong's method. Next, an average wave energy and absorbed energy calculation was applied to investigate the conversion efficiency of the WEC. Finally, the experimental setup is carried out in a water tank under various conditions to evaluate the performance of WEC and validate the modelling. The results indicate that high-energy conversion efficiency of generating electricity from waves is approachable, thanks to the high efficiency of the proposed device.