These rarely have a consistent water level and unless you are familiar with the crossing it is wise to get out of the car to see how deep the water is first.
Some fords have marker posts set into the ground so you can check the water level at a glance. As a rule, any water which will come above the level of the door bottom is probably too deep for the car, although the engine will usually keep running in water up to 60cm deep.
The assumption that the good grip of modern tyres means you are always safe on wet roads in a...