Prepare yourself for the trials and tribulations of one person's attempt to backfill an in ground swimming pool and cover it with synthetic grass. If you're at all interested in undertaking a project like this first please read this cautionary tale.
What you think you may know about synthetic grass is probably wrong and what salespeople tell you about their synthetic grass is probably not all that true either. Do a lot of research and talk to as many people as you can. Bottom line, don't believe anyone... including me.