Abstract: A hydrodynamic power-generating system includes a power plant, a motion-generating subsystem, and a support subsystem for supporting the motion-generating subsystem in a dynamic water source such as a river. The motion-generating subsystem is configured to oscillate and pivot under hydrodynamic force to drive a rod. The power plant is configured to then convert the oscillating drive motion of the rod to electrical power. The motion-generating subsystem includes a pair of spaced beams having upstream ends and downstream ends. The spaced beams are pivotally supported within the water at the upstream ends thereof by the support subsystem. A pair of shafts are connected to and between the beams at the upstream ends and the downstream ends, respectively. A foil is pivotally disposed between the downstream ends of the beams. A trim flap is pivotally disposed at a downstream edge of the foil.