Grand Staircase

The Grand staircase was a stairway for first class passengers (like Jack Thayer) at the RMS Titanic and HMHS Britannic, and sank with the whole ships. The grand staircase on the RMS Olympic was dismembered along with the whole ship in 1930 and is now placed at a hotel in England.

Titanic
The grand staircase has a clock and a glass roof. When the Titanic is sinking, E-deck flooded first. Then D-deck flooded, then C, then B, and finally A. Boat deck was flooding starting 2:11 am. At 2:16, the grand staircase looked sunken from the outside, but at the inside, the grand staircase is slowly being put under. It was so slow that water is at its roof, and it broke, making water fall from the top. It was sunken down quickly.

Britannic
The staircase at the Britannic was improved, like most of the ship. When it sank in 1916, there is no record of what happened at the Grand staircase.