(at around 2h 30 mins) The elderly couple seen hugging on the bed while water floods their room were the owners of Macy's department store in New York, Rosalie Ida Straus and Isidor Straus, both of whom died on the Titanic. Ida was offered a seat on a lifeboat but refused so that she could stay with her husband, saying, "As we have lived together, so we shall die together." There was a scene filmed that depicted this moment but was cut from the final version. It was Mrs Straus who originally said "Where you go, I go" that inspired Rose's same line in the film.
James Cameron went on 12 dives to the actual Titanic himself and found seeing the sunken ship an overwhelming emotional experience. During his first trip, he was so goal-oriented that he managed to film the shots he wanted, but as soon as he was back on the surface, he broke down in tears after finally realizing the magnitude of the historical tragedy he had just witnessed. He spent more time with the ship than its living passengers did.
(at around 2h 35 mins) In the scene where the water comes crashing into the Grand Staircase room, the film makers had only one shot at it because the entire set and furnishings were going to be destroyed.
The scenes set in 1912, i.e. the whole movie except the present-day scenes and the opening and ending credits, have a total length of two hours and forty minutes, the exact time it took for Titanic to sink. Also, the collision with the iceberg reportedly lasted 37 seconds, which is how long the collision scene is in the movie.
(at around 2h 15 mins) Many of the "core extras" used for the movie took on characteristics of actual survivors. One scene where two little girls are loaded onto a lifeboat and the man says, "It's only for a little while" is based on testimony from one of the girls who survived. The man also says in the scene, "Hold Mummy's hand and be a good little girl." According to survivor Eva Hart, these were the last words her father said to her before the lifeboat she was in was lowered.
James Cameron: (at around 1h 9 mins) Just below Lovejoy during the below decks party, with a gray beard.
James Cameron: Standing behind Fabrizio on the deck waiting for a lifeboat when Murdoch starts shooting.
James Cameron: [perfect cut] Several dissolves between the Titanic on the seabed to the Titanic of the past, and the dissolve from the young to the old Rose.
James Cameron: [feet] The shoe at the beginning, Rose's feet while climbing the rail, Jack's feet when taking off his shoes, Rose's and Jack's feet while dancing.