* Water and Electricity Don't Mix: Water is a conductor of electricity. If a plugged-in hair dryer (or any electrical appliance) falls into water, the electricity can travel through the water and electrocute anyone in contact with it.
* Grounding: Bathtubs and plumbing are often grounded, meaning they are connected to the earth. This makes them very effective conductors of electricity. If electricity flows through the water and into the tub, it can easily travel through a person's body to the ground.
* Outlet Proximity: Bathrooms often have electrical outlets close to sinks and tubs, increasing the risk of an appliance falling in. Even if an outlet has a GFCI (Ground Fault Circuit Interrupter), which is designed to cut power quickly if it detects a fault, it might not react fast enough to prevent serious injury or death.
In short, never use electrical appliances in or near a bathtub or sink filled with water. It's a life-threatening risk.