If your vehicle starts to hydroplane it means that your vehicles tires have lost contact with road.
Remain calm and slowly ease your foot off the gas pedal to slowly decelerate and wait for the skid to stop while you steer the vehicle in the direction you want the vehicle to go.
To lessen your chances of hydroplaning you should drive slower in the rain when you can safely do so which can prevent your vehicle from going out of control when the road is wet.