Abstract: A fluid foil for use in a marine propeller having an upper surface with a uniform, continuous convex shape commencing at the leading edge and terminating at the trailing edge of the foil section and a lower foil face having a convex shape extending from the said leading edge to the foil mid/chord position and having a concave shape extending from the said mid-chord position to the said trailing edge. An effective pitch line extending from the foil leading edge to the foil trailing edge is intersected tangentially by the concave shape of the lower foil face.