If you feel like a swim, Club Mediterranée a few metres from the Djema al Fnaa provides a pool and lunch for £15. There are a number of pools in the Palmeraie just outside Marrakech. Details are available for you at Riad Lucas.
Further afield, in the Atlas foothills, is La Roseraie. About ane hour’s drive from Marrakech it has a lovely pool and a good restaurant.