a cover assembly for a swimming pool and which can be raised and lowered , the cover assembly comprising a frame which is relatively rigid , a covering material which is supported by the frame , and a plurality of extendable and retractable leg members which are associated with the frame such that extension of the leg member causes the frame to be raised and lowering of the leg member causes the frame to be lowered , at least one leg member being powered to enable the leg member to the extended upon demand .