new liner

[TMan]

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!

[madwil]

The divots can be from sand washing some, but can also be from uneven settling; before replacing the liner, I'd back fill a small amount of lime and smooth- lime works well to completely fill the settled spots and redistrubute weight in house foundations, assume would work well here also.
another trick used in building is to fill with mortar mix- will compress in hollows, and will harden with time to prevent erosion some... not recommended for those not familiar with concrete and/or tile beds!
Good idea to use old pool liner as a protector for the new one!