Abstract: A device to convert wave energy into mechanical energy, comprises a buoyant structure whose upper portion is in the region of wave action but whose lower section is below the region of wave action, so that the water adjacent the upper and lower sections of the structure has vertical movement relative to itself. This relative movement is used to rotate a vertical shaft having radially extending horizontal axles on which panels are pivotally mounted. Ballast and/or floats are used to impose on the panels a bias tending to maintain them horizontal. The relative movement of the water is used to impel fluid vertically relative to the panels in alternatingly opposite directions; and the bias imposed by the ballast and/or floats thus causes a planing wing action of the panels which impels the shaft in rotation in one direction regardless of the direction of the movement of the impelling fluid. The floating structure can rise and fall with the waves (FIGS.