A phone charger can be incompatible and can start a fire?!
Princess’s safety handout is at https://book.princess.com/html/personalizer/downloads/pdf/Safety_Information.pdf It has a warning not to bring a surge protector on board, and I found the Coast Guard warning document that explains that cruise ships may be wired differently from homes. But below it is Special care should be taken when charging portable electronic devices, such as mobile phones, as these may not be compatible with the ship’s electrical system and can result in damage to the charger or start a fire. If you are unsure, consult the Guest Services Desk for assistance. Um, is this really a concern? Is there a way to