Abstract: A new and useful propulsion apparatus for use by a swimmer is provided. The propulsion apparatus comprises (a) a support structure configured for connection to a swimmer's foot, and (b) a fin connected with the support structure by a flexible coupling in a manner that enables the fin to be stroked in alternating downstrokes and upstrokes by flexion of a swimmer's knees. The flexible coupling is configured to enable the fin to rotate in a first direction relative to the support structure during a downstroke, and the propulsion apparatus has a mechanical stop for limiting rotation of the fin in the first direction to physically set the angle of attack on the fin during a downstroke. The flexible coupling comprises an elastic suspension extending between the support structure and the fin, the elastic suspension being configured to (a) allow the fin to rotate in a second direction opposite to the first direction during an upstroke and (b) dynamically set the angle of attack during an upstroke.

Abstract: A new and useful propulsion apparatus for use by a swimmer is provided. The propulsion apparatus comprises (a) a support structure configured for connection to a swimmer's foot, and (b) a fin connected with the support structure by a flexible coupling in a manner that enables the fin to be stroked in alternating downstrokes and upstrokes by flexion of a swimmer's knees. The flexible coupling is configured to enable the fin to rotate in a first direction relative to the support structure during a downstroke, and the propulsion apparatus has a mechanical stop for limiting rotation of the fin in the first direction to physically set the angle of attack on the fin during a downstroke. The flexible coupling comprises an elastic suspension extending between the support structure and the fin, the elastic suspension being configured to (a) allow the fin to rotate in a second direction opposite to the first direction during an upstroke and (b) dynamically set the angle of attack during an upstroke.