I think those heating comments were based on a steel sub which might implode by crushing the hull, trapping air behind the steel and overheating it.
Original heating comment, from form Nuclear Sub officer:
The Titan submersible suffered a violent collapse inwards deep underwater in the North Atlantic.
www.bbc.com
But I think the CF probably just disintegrates and it would be water instantly dissipating the heat, so I would not expect bodies to be cremated.
The TNT comment were from various physics nerds calculating energy release from implosion, like this one:
Like many I’ve been captivated by the Titan story. I’m wondering a few things: 1. Was a shock wave cause by the implosion? 2. Would marine life have been killed similarly to “fishing w/ dynamite”? Kill radius? 3. A TV talking head claimed the inside of the vessel would have heated to “a temp...
www.physicsforums.com
Regardless of the actual numbers. There is Enormous potential energy released in a tiny fraction of a second when a deep see hull implodes, there will be a big shock wave rebounding out.