My pool got those potholes supposedly from the sand washing out a bit during heavy, heavy rains. It didn't compromise the integrity of the pool but did show and could be 2-3" deep on a few. Anywho, somewhere I read to take an old bowling ball and do some diving, gently pushing the sand around them to smooth them. Of course I didn't have one and the next tip was for those of us lacking a spare bowling ball: Wrap a 3 or 5lb sledge hammer very good with a towel giving a heavy blunt side. I took that down in the pool and with very little massaging the divots were gone!