I drove mine through water lower than that (which everyone was driving through fine), i.e. it wasn't up to the bottom of the car, but it presumably contacted it as the car made a wave driving through.
Drove home from work later that day, kept hearing this sloshing noise, then went to get something out from under the seat and there was 1" of water under there.
To cut a long story short after taking ages to dry the car out I discovered it has two holes (one either side) which allow water to freely enter the car if it reaches that level... which the garage were as shocked about as I was!