Yes - I think that's probably a good summary - the question is: why didn't an alarm sound when the cage hit the water? Was there no alarm system in place or was there one in place and it failed to work? The same goes for an alarm system on the 11 and 12th levels... you'd think there'd be some sort of system to notify the surface if water levels go beyond a certain point.
I also can't help wonder how fast the cage descends down the staft. There's a system in place for the guys in the cage to communicate with the operator... obviously they had very little time to do so. It must have been seconds before the cage was submerged.