A surge oscillating flap-type device is one of the most usable wave energy converters for extracting power from ocean waves. The relative movement of the piston and cylinder of a hydraulic power take-off system attached to the vertical flap and the base is responsible for converting the mechanical oscillations of the flap into hydraulic pressure in a bottom-hinged flap-type converter. This study proposes a new design to investigate its hydrodynamic characteristics and output power, including a vertical buoyant flap hinged to a horizontal gravity flap. This analysis is done by solving the governing Laplace equation through the BEM approach in ANSYS AQWA. The steady-state relative displacement between flaps is obtained through a time-domain analysis, which is used to calculate the output power. The results show that the proposed floating design can extract power from ocean waves at offshore sites. The WEC is designed to match its power resonance periods with the most wave dominant periods of 8-10 s.