With regards to electrical equipment in the bathroom, a friend installed a very fancy cabinet in his shower room. The cabinet formed from stainless steel was fitted with a Bluetooth audio system and heating pads to ensure the mirror on the front remained fog free. The system appeared to be working fine, until he touched the cabinet while shaving and received a shock. I was asked to investigate.
Everything in the cabinet was double insulated and insulation tests showed no leakage between the power leads and the cabinet. Tests also revealed that the cabinet itself was not earthed because power had been tapped off an old lighting circuit, which was so old it was not provided with an earth connection.
What was happening was that steel case of the cabinet was coupling as a huge extra turn to the low voltage transformer supplying power for the audio system. The cabinet was gradually charging up to 300 volts or so while it was in use with respect to earth. Touch the cabinet and you got a brief but severe shock, especially standing on a damp floor with wet feet! There was no electrical connection between the cabinet body itself and the mains, but still an electrical shock risk existed.
Once the cabinet was connected up properly to the mains supply with the cabinet bonded to earth and all the other bathroom appliances, everything was fine. This involved some heavy duty drilling through a double wall to route a proper power cable, which is why my friend had taken the easy option of tapping into the lighting circuit. Everything was working just fine until he used the shower and the cabinet had been powered up for some time.
Even simple electrical work carries risks if you don't fully understand what is going on.