When a car hydroplanes the most important thing to remember is not to panic. First, do not brake or accelerate suddenly. Since hydroplaning is a loss of traction to the front tires sudden braking slows the front tires but locks the rear tires which can cause a spin out. Also sudden acceleration could pull the vehicle straight ahead which could be dangerous if the vehicle is pointed toward the edge of the roadway.
Do not use cruise control in heavy rain; your vehicle will recognize the build up of water as a slow down and ask for more power, which may lead to problems.