standard 20x40 in ground concrete pool has a foot long 1/32 hairline crack in one of the corners starting from the water line down.
losing about an 1" per day. this is more than evaporation alone so it could be leaking.
* what product/method is used to repair this? lowering the water level a foot or two for proper repair is a possibility.
a very light blue colored product to better match the concrete finish so that the repair is less obviously would be a big plus.