Swimming pool covers are installed to retain heat when the pools are nut in use. Covers for pools of irregular shape (non-rectangular, non circular) are expensive to install and cumbersome to use. A great deal of energy is thus wasted from such pools. This proposal concerns a new concept for swimming pools. Floating plastic spheres are used to cover the pool. This both retains heat at night and when not in use during the day, and also absorbs solar energy. The remotely operated mechanism for applying the spheres and for removing them ensures ease of use, and this maximises heat saving. Research is required firstly to optimise the size and materials of the Spheres and to provide design information, and secondly to develop a prototype device for applying and extracting the spheres from the pool surface.