Just last week I was in deep muddy water up to the edge of the front of the hood, didn't really have an option as a friend needed recovery from that direction (although i didn't expect it to be that deep) In order to back out I was at the rev limiter going back and forth several times as the bottom was soup. I ended up with enough resistance on the fan to toss the belt and once everything was back together and the rad was cleaned a bit (I keep a water/air fire extinguisher for just this sort of thing in the jeep) it started to over heat. I found the fan clutch had been nuked by the resistance of the water. I didn't enter an high engine speed, i crawled in at idle, high rpm didn't happen until I was trying to back out. So yes, deep water can kill a fan clutch, this one wasn't brand new but my jeep doesn't see much mileage as it's a trailer queen these days so I suspect it didn't start off as clapped out. This is with a ford 10 blade fan, and a ford explorer severe duty /w AC clutch.