people are covered if they drive through a flood and damage the car as long as they have comprehensive cover.
I know of two people who have had this happen in the past couple of years, one had a new engine fitted (Golf R32) after a deep puddle turned out to be very deep puddle, the other had the car (Porsche 944 turbo) fully paid out as the water went from being 4 inches deep when he drove into it to being 4ft deep by the time the rain stopped an hour later.