The first-order linearized hydrodynamic equations of motion are solved to obtain the velocity potential, which is composed of a wave part and a spatially transitory part. Characteristics of generated waves far away from the wavemaker are analyzed as to the wave profile, flap stroke, water particle excursions, and power consumption of the wavemaker. The importance of the spatially transitory part is discussed with regard to the role played by the inertia pressure, which gives rise to added inertia of the flap. Surface elevations very near the flap are found. The hydrodynamically induced torque and the total hydrodynamic force on the flap are computed. The computed results seem to be well explained by the differing behaviors of the normal pressure and of the inertia pressure with increasing water depth.