Electrical shock

My son who lives in MD bought a house with an inground fiberglass saltwater pool. This summer when in the pool and you touch the cement or if you are wet and touch the cement you get a light shock. He has turned off all power to his house and pool and it still happens. He has had pool and electrical people out and no answer yet. They did measure the output and it was like touching a battery. The other day when someone new was out it was not doing it. Could it be coming from another house? Any suggestions or answers would greatly be appreciated.