Downflooding points include all openings, irrespective of
size, that would permit passage of water through a water/weathertight
bulkhead or deck, e.g. opening windows. Downflooding points exclude
openings kept closed to an appropriate standard of water/weathertightness
at all times other than when required for access or for operation
of portable submersible bilge pumps in an emergency, e.g. non-opening
windows of similar strength and weathertight integrity to the structure
in which they are installed.