Some fresh water flood cars can be saved if the water wasn't too deep, but virtually all salt water flood cars are totalled. Even if you can get the car running and dried out today, nobody knows what the salt will do to wiring and computer modules a week, a month, or even a year down the road.
In NY and probably in other states, a flooded car must be labeled as such on the salvage paperwork, and on any title that may subsequently be issued.
I'm retired from Allstate. I spoke to a friend of mine who works in their total loss unit on LI. As of last week they had about 18,000 cars that needed to be picked up.