ANSWER: Driving in the rain brings a lot of issues to many drivers as different drivers react differently when they feel their steering wheel slipping away from their hands.
Panic behind the wheel creates different issues for different drivers.
My best advice is for the person driving to immediately shift into a lower gear (in an automatic car, shift to D1 if possible or at least D2). Then gently brake and steer with confidence.
If you have been driving too fast and you start aquaplaning, then there is little you can do and just brace yourself for impact.