Abstract: A buoyant swimming pool cover in the form of a flexible lightweight sheet comprising a large plurality of hollow buoyancy cells spaced apart over the sheet, there being a plurality of drain apertures distributed over the sheet in areas thereof not occupied by the buoyancy cells and serving to allow rain water to flow through the cover into the pool. Best results are achieved when the configuration of the upper surface of the cover presents depressions serving to direct into the drain apertures any water falling onto the cover. Advantageous embodiments are in the form of a lamination of at least two polymeric films at least one of which has been thermoformed to provide generally cup-shaped portions which are closed by another of the polymeric films. Since water cannot collect in any substantial quantity on the cover, the cover can be very lightweight and is always easily lifted off the water, without any dirt or debris which has collected on the cover being carried into the pool as the cover is removed.