No way could that small door have supported bothe of them.
However, the Jack character would have easily survived if he had floated on Kate Winslet. She’s a substantial young lady.
The director called her “Kate Weighs-a-lot.” But in 1912, it was probably stylish for a woman to be heavier than what’s considered ideal now.
She had enough natural insulation to survive the water for a couple of hours.