The Titanic was designed by the Irish shipbuilder William Pirrie and built in Belfast, and was thought to be the world's fastest ship. ... Because four of these compartments could be flooded without causing a critical loss of buoyancy, the Titanic was considered unsinkable.

Who originally said the Titanic was unsinkable?

Franklin announced ” We place absolute confidence in the Titanic. We believe the boat is unsinkable.” By the time Franklin spoke those words Titanic was at the bottom of the ocean. It would seem that the White Star Line President was also influenced by the 'myth'.

How did the unsinkable Titanic sink?

The immediate cause of RMS Titanic's demise was a collision with an iceberg that caused the ocean liner to sink on April 14–15, 1912. While the ship could reportedly stay afloat if as many as 4 of its 16 compartments were breached, the impact had affected at least 5 compartments.