Most people know about what hydroplaning is, but not how it works and how to prevent it, or how to stay in control if it happens.
What happens when you are hydroplaning? The car's tires are lifted off of the road by the water. This happens because of the way water moves as it is pushed by the tires. If the tires can't push enough water out of the way, the pressure builds up and lifts the tire from the road, resulting in a complete of friction and as such control.
What should you do if your car starts to hydroplane? Nothing. Don't turn, brake, or accelerate, as that can just cause the car to spin out. You should just maintain speed and direction until the water stops. It sounds counter intuitive, but its the best solution to the problem.