Pool leak

gunite pool leaking 1/2" water per day. Water drops below skimmer, but water remains in skimmer baskets. Leaks when pump not on. When main drain valve open, loads of bubbles in pump and shooting from return jets. When main drain valve shut and just running skimmers, no bubbles and stream from jet bubble free. Cannot find source of water loss. Recently had deck redone around pool. Workers damaged skimmer line pipe in 2 places which was repaired. Continuing to monitor the water drop. If it continues, my choices are main drain or plugs in deep end. If water stops below skimmer, I have more leaks in skimmer line pipe. Light fixture looks ok. Pool was re-marble dusted last year. Hard to believe it could be structural.
Very aggravating to say the least.