3 of the backup oxygen supply were manually turned on after the "explosion" which was really more of a depressurized expulsion and some fire. The ?pilot? also tried maneuvers. Some of the crew therefore were possibly* alert and awake at least (others probably passed out), possibly right until impact with the water, and then instant death.

But it all happened in a few minutes, and mostly they would have been hyper focused on their training and fixing the problem.