Rose’s gown was far too light
Kate Winslet not only nearly drowned while filming Titanic, but she also developed hypothermia, which we can understand. She was one of the few actors who were not permitted to wear a wetsuit during the water scenes, and she spent the entire time aboard the ship dressed in a slip dress. Winslet almost left, but James Cameron persuaded her to stay. The paper-thin clothing could hardly have kept her warm, and she showed no signs of hypothermia, unlike Winslet.
Boiler room escapades
One of the most romantic scenes in the film (or any film) is when Jack and Rose find themselves in the boiler room and enjoy a hot kiss. While that sounds great in theory, the reality would have been quite different. This would never have been permitted in real life because it is completely prohibited due to its extreme hazard.