" believe him but, 4 feet of water ? " An ordinary Blazer or PU will go through four feet of water as long as the vehicle does not stop, or is NOT going too fast. 10 to 15 MPH will get the vehicle through, the exhaust gas pressure, if contant will keep the water out and the water flows down around the engine ( not through the radiator) withput impeading the fan. If the vehicle pauses or stops and water gets aropund the fan, that usually throws ware all over the engine and it gets into the air feed for the carb or FI. One can also dismount the fan belt for a very short run if this is a problem, the engine runs off the battery.
I think our man probably knew this fact about the water, being a military historian. It would be great to ask him though!
I found out this trick by 4 wheelin in the Canadian outback when I ran a survey crew with a mining exploration company.