This definitely sucks. Submarine lost.

I doubt they had time for even a moment of panic. If it was some failure that left the hull intact, they should have been able to blow ballast and surface. I fear it was a catastrophic failure of the pressure vessel and they were squashed almost instantly. But, all pure speculation.
Did you watch the transcript video ?

They had haul failure sensors that were going red for like 20 minutes. And cracking sounds. It was scary af


And some signs point to the vessel not being buoyant and having to use props to surface (lol)
 
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