"a waterproofed duffle bag on the outside of the vehicle could be a lifesaver."

I agree completely, if he had a dry bag like watershed or DUI or something of that nature that is a real dry bag and not a rollup good to 1 foot of water and had some replacement cloths,socks and shoes he would have made it providing he kept the bad near him. A watershed bag is good to 200 ft and some to 300 ft and cheaper than DUI. It's good in any water/katrina/boat cruise/ice storm environment.

http://drybags.com/home.html