Abstract: A swimming device has a body platform with straps for the arms and body of a swimmer. Cylinders extend longitudinally on the platform and are open at their forward ends and have restricted outlet nozzles in the rear. Pistons are slidably mounted in the cylinders, and cables are secured to the pistons and to foot stirrups. The pistons are provided with flapper valves which open to permit fluid passage upon forward propulsion of the piston, and close to prevent such passage when the piston is on its backstroke, thereby forcing a water jet from the piston to propel the platform and swimmer forward.