By way of overview and introduction what is disclosed is a fin structure for use with watercraft that is configured to provide lateral stability and generate hydrodynamic lift. The fin structure has a first end that can be connected to the underside of a hull. Two sidewalls extend away from the first end down into the water. As the side walls extend away from the hull, they also first diverge relative to one another and then converge to form a generally diamond shaped fin structure that is symmetric across the longitudinal axis and has an opening in between the sidewalls. Preferably, the sidewalls have a cross-section profile with an outer surface having more curvature than the inner surface. The shape of the fin structure provides lateral stability, hydrodynamic lift and maneuverability.