In castles maybe but not in modern buildings flood water would come
into a citadel one door at a time. They were built on hills for one
thing and did not adhere to conventional building codes for another.

A comment on Real Rescues just now had the head teacher of a young
children school telling is that she was surprised and alarmed that the
water came in through all the doors at the same time.

At least it showed the builders had got the levels right.