Patent ID: 7281963

Claim:
An energy-conserving swim fin, comprising a blade extending from a front portion of a foot pocket of a swim fin, with at least one spring longitudinally fitted at an appropriate position on the blade; wherein the spring provides two different force coefficients as support is provided when force is inwardly applied to two ends of the spring and extensibility is provided when force is outwardly applied; whereby during the course of a two-stroke alternate flapping motion of the swim fin, the swim fin forms an angle against the water when kicking the water to push forward, thereby achieving a propulsion effect, and extensibility of the spring produced during a restoring motion of the swim fin enables the blade to form an angle that reduces resistence to the water, thereby achieving effectiveness to conserve energy and rapidly return to original state; and further wherein the blade at a location of each of the at least one spring is respectively provided with a columnar body, and the spring is respectively installed in slots defined at appropriate positions on the columnar body.