Well, it was sometime between 21:15-12:45 am when the bulkhead between boiler rooms 5&6 collapsed according to "A Night to Remember" by Walter Lord. Boiler room 5 was the last room known to be damaged (about a 2 foot "gash) past the watertight door theat separated it from Boiler room 6 (foreward) and Boiler room 4 (aft). Funny thing is, when the water reached Boiler room 4 at 1:20, it came up from benaeath the plates in the floor. That's a quite a bit before the "wave" that came near the final plunge.