Does low tire pressure effect a car hydroplaning?

Absolutely, and if one tire is more flat, thus wider, it will or could cause a spin out and loss of control.

It is directly related to the square root of the tire pressure. According to testing cited by the NTSB (National Transportation Safety Board) the speed at which a normal tire will begin to hydroplane is 10.35 x the square root of the tire pressure. So, if the recommended tire pressure for your vehicle is 36psi, the speed at which you can expect to hydroplane would be 62 mph. Let that tire pressure go down to 25psi and you're hydroplaning speed drops down to 52mph!