Pool covers serve different needs. Thus, depending on your requirements you can choose:
Safety Cover, Very useful if you have small children, or if you are away for a long time and wish to be absolutely sure that even if someone reaches your pool there will be no unexpected events. You can even stand or walk on the cover.
Isothermal cover, to protect from the cold and maintain water temperature. Especially, if you avail a heated pool, or you're in an area that temperature falls sharply during the night time, it is necessary for you
Winter safecover to cover your pool the whole winter, for your cottage, or main house, if you are not using the pool in the winter. Protects from dirt, leaves, small animals.