Just don't risk it. That said, I did the other day in my local flooded area as all access roads were flooded and I had to choose what I assessed as being the less deep of all the evils. My guess it was at about 6-8" deep as it was sloshing up to the bottom of the sill and judging by the low front it's not quite as low, thankfully, as I was concerned about. On top of that, cautiously crawling at less than 5mph helped minimise displacement/waves.