Here are my thoughts in relation to some of the replies to this thread, sorry if it's a bit TLDR (Too Long Didn't Read)
Petrol vehicles, the ignition circuit can short in water causing the engine to die. Usually by the fan behind the radiator spraying water over the HT leads.
Diesel and petrol vehicles, hydrolock by sucking water into the engine, or exhaust getting blocked with water (keep the engine revs up)
Land Rovers and other 4x4s can still suffer from this too, but the higher ground clearance plus driving technique are the key to wading. Yes, you can get raised air intakes or snorkels for these vehicles. There is a subtle difference. Raised air intake is used to raise the air intake, typically used in dusty/desert conditions to reduce amount of dust/sand sucking into air intake. Not waterproof. Snorkel, also raises the air intake, but is waterproof, and can be used to wade deeper water. Plenty of 4x4 owners out there with raised air intakes that think they can safely wade in water as they don't know the difference.
The key thing is driving technique. Not too fast, and not too slow, but enough to create a bow wave. This will cause the water to be higher at the front, but is then lower than the actual water level around the front wheels allowing a vehicle to wade through water deeper than the vehicles maximum wading depth (0.5 metre for a standard Land Rover Defender)
However, this ford is in flood, which means the water flowing through it is flowing faster than it normally would. Water doesn't have to be very deep at all to lift a car if it is flowing fast enough. The MG4 demonstrates this, and was definately floating at one point, but either it took on more water and sank, or hit some higher ground and regained traction.
Other potential hazards with flood water, you do not know what is in the water, you could hit a large tree branch, rocks, etc washed downstream. Flood water should be treated the same as raw sewage as sewers and drains will have overflowed in the flood. If the flood is on a road rather than a ford, then drain covers could have lifted, and if your wheel drops into one of those, then you're stuck. If you have to walk in flood water, then an open drain would suck you in and that would be it.
From the training I have the guidance is clear, do not drive or wade in flood water. Find an alternative route. There are too many examples of people losing their lives as a result of driving through flood water. Even experienced drivers can be caught out. For example, there was a lady who drove through a ford in her Land Rover every day, but drove through while it was in flood. Her Land Rover was swept away, and found 5 miles downstream wedged against the side of a bridge. Unfortunately she drowned.
As far as I'm concerned, every driver going through that ford in flood is an idiot.
