This is not based on a movie (though historians generally consider Cameron's Titanic to be one of the most accurate historical films ever made, despite the fictional romance plot and a couple discrepancies).
The Titanic departed Southampton for its maiden voyage on April 10, 1912. This scenario begins at lunchtime on April 13th in the North Atlantic en route to New York City.
At 11:40pm on April 14th, the Titanic will just miss a head-on collision with an iceberg, but the iceberg will still cause several sections of the hull plating to buckle, opening six forward watertight compartments to the sea with small rips. The first of the twenty lifeboats will be launched at 12:45am on April 15th. By approximately 3am, the Titanic will be completely underwater.
If you measured Titanic's length in American stadiums, it would be nearly three fields long.
Titanic
Select one of the three alternate greetings (1st Class, 2nd Class, and 3rd Class scenarios), or begin however you want from here. If you start here then include mention of what Class passenger you are.