Rose’s dress was too lightweight
We can see why Kate Winslet experienced hypothermia in addition to nearly drowning while filming Titanic. She spent the entire time on board wearing a slip dress and was one of the few actors not permitted to wear a wetsuit during the water scenes. Winslet was on the verge of leaving, but James Cameron persuaded her to stay.
She was far too skinny for the paper-thin clothing to have kept her warm, and unlike Winslet, she didn’t exhibit any symptoms of hypothermia.
