This invention relates to a cover structure for a swimming pool.  The cover structure can be formed of an open weave net material, in which case the cover serves primarily as a safety device to prevent persons from falling into the pool.  Alternately, the cover structure could be formed of a non-porous fabric or flexible sheet material, in which case the cover could in addition serve as protection against leaves or other debris from entering the pool.  The cover could also serve to minimize water evaporation losses, as well as maximizing the solar heating action obtained with some cover materials.  The term "cover" will be used herein to designate either a non-porous flexible sheet-like cover or a porous open weave net-like cover. 
A principle aim of the invention is to provide a cover that can be opened or closed with a relatively small energy expenditure.  In its preferred form the cover is attached to two laterally spaced cables running within tracks along opposite sides of the swimming pool.  Cable motion in one direction draws the cover across the pool opening to a closed position.  Cable motion in the other direction draws the cover to an open position.  Comparatively little effort is required to move the cable back and forth. 
Electric motors may be used to open or close the cover.  Alternately, the cover may be opened or closed by the use of rotary hand cranks.  When electric motors are used, such motors may be remotely controlled with radio signal sending-receiving equipment.  Preferably the power supply for such equipment includes a key-operated switch, such that the pool owner is assured that the cover will not be operated unless the owner is present.  In addition there is a stationary hard wired open/close switch that is also activated by the master key switch. 
In preferred practice of the invention a safety device is associated with the leading edge of the cover, so that if a person (or object) should be touched thereby while the cover is being closed the safety mechanism would automatically cause the cover to retract to the open position, thereby preventing a person or object from being trapped against or underneath the cover.