Waterlogged Bonnie

My 99 Bonnie SE voltmeter dips to about 11V and all light dim after going through puddles in heavy rain. Things recover in a short time, but if more puddles are encountered, it will repeat. I suspect belt is slipping on pulley, but I would think the battery would hold the voltage up even if alternator is slipping. I have heard belt squeal during this condition. Has anyone else had this happen?

dont drive through big puddles with any car, no ground clearance. When you get water on the belts it will cause a problem, i had a hose blow and spray antifreeze all over the belts and i had the same problem.