You also have to consider the bouyancy of wheels and body panels not yet filled with water which will kill traction, or if the water is moving it doesn't take a lot to push vehicles around.

Most cars crossing water don't get stuck because the intake is blocked by water but because they either floated or get pushed away by the flow (or slammed into the water hard enough to break stuff). If you maintain forward movement and dont float most cars will keep going in water 4-6 inches above the intake height because of the wake and bubble of the engine compartment. You only really benefit from a snorkel if you are offroading through water where there may be unseen holes because submerging your entire engine and drivetrain that deep is still a horrible idea even with a snorkel.

Also if you don't have a direct motor on each drive wheel you still have to worry about water entering differentials and transfer cases even if the electronics are perfectly sealed.