I hit a deep puddle of water 6+ inches at about 20 mph and the lights dimmed and the volt meter went to zero after about a quarter mile everything went back to normal.
Voltage drop after hitting a puddle on passenger side on 1993 Jeep Grand Cherokee
Sounds like water either got on the belt causing slippage till it dried and now should be ok or water got in to alternator or connections till drained and all is ok for now. If you have no more problems then keep driving. I suspect the belt was it.