When I had my Altima a few years ago I once turned a corner and realized I had driven into a flood zone. It was raining heavily and the sewers were unable to handle the water. You could not tell that you were entering a "puddle" because the rain was coming down so hard it that everything looked like blacktop and the police had not arrived yet to block off the street from unsuspecting motorists like myself. The car actually floated a few feet, stalled out, and luckily ended up with all 4 tires still on the road. I had to get out, with water rushing in the door, and with the help of some people in a nearby house, pushed the car to somewhat drier land. After about 15 minutes I was able to start the car, but it would probably have been better if I let it be.   The engine was damaged and it cost me quite a bit to repair it.    This incident was another factor. Not that I intend to ford rivers, but I do like the comfort of knowing I am a bit higher up.   20 inches does seem a bit extreme.