It really is amazing just how little water it actually takes to float a modern 4 wheel drive vehicle.
Engineers at the University of New South Wales used a test tank to replicate scenarios face by stranded drivers.
Here's the link to the video and the full article and remember if it's flooded, forget it.
Source: http://mobile.abc.net.au/news/2016-06-18/research-shows-cars-deadly-in-floodwaters/7522798