Abstract: The device of the present invention comprises a footwear member such as a sandal, attached to a swimmer's foot by strap or thong means, and a forwardly projecting fin shaped frame member, fixed to the sandal and including a plurality of longitudinally extending vanes, pivotally attached between the opposed end wall portions of the frame. When the swimmer moves the device inwardly toward his or her body, the vanes open in response to the reactive forces of the water, permitting the water to pass between the vanes; when the device is moved away from the body, the reactive forces of the water close the vanes relative to each other, creating a condition whereby the swimmer is propelled forwardly through the water.