A swim fin and a method providing thrust from a kick by a swimmer are disclosed. The swim fin includes a swim fin for use by a swimmer comprising a foot pocket adapted to receive a foot of the swimmer; a blade extending from the foot pocket; a biasing system configured to allow the blade to bend within a narrow range of angles of attack under a wide range of loads. The method comprises providing a swim fin comprising a foot pocket, a blade, and one or more non-linear ribs that extend generally perpendicular to the blade. The method also comprises bending the blade relative to the foot pocket about an axis and controlling the bending of the blade by providing varying resistance by the non-linear ribs.