An apparatus for providing stability and reduced turbulence to a surfboard that is moving along its longitudinal axis includes at least one opening that passes through a surfboard fin when viewed from the side. When viewed in cross-section, each opening includes an optimized tapering profile that extends around an interior perimeter of the opening which reduces turbulence, and thereby lessens drag when the surfboard is moving forward in the water in a direction that is parallel to a center longitudinal axis of the surfboard and fin. The apparatus also significantly reducing side to side resistance when turning the surfboard.