Abstract: An apparatus for generating a control current flow in a pool, comprises, a continuously operable electric motor which has a rotatable drive shaft which is connected to an electrically operated clutch. A rotatable propeller drive shaft is disposed alongside the clutch and is engageable with the clutch upon actuation thereof to rotate a propeller affixed thereto to produce a current flow in the pool. The device includes means for sensing the level of the water and for operating the clutch either directly upon changes of level or after a time delay so that it selectively engages and disengages from the propeller drive shaft. The engagement for rotation of the propeller at selected intervals in accordance with the level of the pool produces a wave flow within a few minutes.