I do bot know the specifics, but I think the 96 hr window is being optimistic. That figure is probably provided under normal operation and not the increased respiration rate of a sub full of panicked individuals. Realistically, I think they have significantly less.
The best case scenario is the sub surfaced and experienced mechanical issues and is floating along somewhere. However, I think that is unlikely. If they have not been spotted, radioed for help, used a satellite phone, or activated an emergency beacon by now, then they probably never surfaced. I would find it hard that sub was damaged and all of those safety measures failed too.
The "best worst case" scenario is that the sub is disabled near the wreck. This will be the fastest path to locating and recovering the vessel. But the outcome still looks grim.
Slightly worse is if the vessel is stuck on the wreck and needs to be freed before recovery.
The absolute worst case is the sub is nowhere to be found when the wreck area is searched. At that point just hope an unfortunate miracle happened and the "best case scenario" is occurring. I am hoping for the best, but sadly, I have a feeling the worst outcome for the crew and families is likely to unfold.
