Not an expert on the subject but one side of my pool is out of the ground due to a drop off. I did my own build and one of the contractors told me that is an issue with that type build. I sprayed the pool shell inside and the exposed outside of the shot-crete prior to tile/plaster, etc. to avoid that situation with a water proofing substance. This is the second question I've seen in two days on the subject and have not seen a response. I would contact your builder with your concern and hopefully someone with experience will chime in. It could be penetrating through the tile or plaster.