Sinking of the stern section

[Chung Rex]

I wonder, if the stern and bow separated quick enough, the stern may stay afloat at horizontal direction(therefore the waterline stays below portholes and any openings) and several hundred more people could have survived. If that happened, it would be depicted as a miracle.

However, even if the stern settled at vertical position, it was doomed as water could enter through non-watertight parts.

 

[TimTurner]

Possibly, but the stress of the bow and stern ripping apart probably irrecoverably damaged the stern. The watertight bulkheads at the front of the stern probably wouldn't have kept the water out. I believe the stern basically did settle out horizontally, but it wasn't watertight, so it began flooding. After that, it tilted vertically again and sank.