battery voltage drops after driving through standing water

Battery voltage dropped and power steering seized after driving through standing water. Alternator was replaced after the first such incident. Since then, in the past month, the problem occurred on several other occasions, although on only one occasion did the DIC advise Battery Charging System required service. When the car was taken to the dealer after the third such incident, I was advised the Computer system had no record of the advise to the DIC that the Battery Charging System required service. Dealer advised not to drive through standing water, which, I guess, would include not driving in the rain. Interesting solution. I was also instructed not to look to the internet for possible solutions. What am I? a child? I live in Southern California, where we have little rain, these days, so possible this will not be a big problem.....but feels like a big problem anyway.