Well, I wouldn't say that there is no concern about fording through water with a vehicle. If you notice on the picture that there is a wave infront of the runner. This wave pushes quite a bit of water away from the motor and tranny initially. Motors are for the most part a sealed system ie oil in the oil pan, pressureized fuel lines, closed vacuum systems, etc. Thats not to say that if the air intake tube is below water line it will suck in water and hydrolock the engine. Electronics can be damaged if water is too high and they are not waterproofed and sealed. Also, you must extend the front diff, tranny, and rear diff breathers to above water levels or risk sucking water into these components as they are hotter than the water they are submerged in. Now for that particular picture, I am assuming that the driver is constantly moving at a conservative speed, thus keeping most of the water ahead of the vehicle and below the top of the engine.
