The Titanic was engineered in such a way that the sealed water-tight compartments were not water-tight on top. So like an ice tray, once one compartment filled up with water, it just spilled over the top and begin filling in the next one. As the Titanic's water tight compartments filled up, the ship began to tilt as the water made the ship heavier.
Evidently the ship broke into two pieces as it sunk.
During that time period the owner of Whitestar Lines stated for the media that "Not even God could sink this ship." My grandparents and others of that generation felt that he had uttered a curse that brought tragedy to the ship.
The ship did not slow down when warned of ice ahead. When the iceburg that struck the ship, the crew attempted to turn. If they had sped up and hit the iceburg head on, the tragedy may have been averted. Evidently the ship brushed along the iceburg for the entire length of the hull just below the water line. This long gash let in tremendous amounts of seawater. The passengers simply felt a small tremble or quiver, nothing of note.
It was certainly the greatest maritime disaster of the 20th century.