If you have a sealed exhaust (no leaks) you
won't get water into the engine, too many
places air (exhaust) gets trapped and won't
let the water through, first one is the U bend
that goes over the rear axle, prevents water
from going too far, next is the up section from
the cat to the manifold.
I've been half way up the door in water, about
3 feet, funny it sounds like a boat, no problems.