Kate Winslet reveals some previously unpublished secrets from her experience filming “Titanic.”

During a panel discussion at a preview of her upcoming film “Lee” on Monday, the 48-year-old British actress spoke about the infamous scene from the 1997 film in which her character Rose floats on a door in the Atlantic Ocean while Leonardo DiCaprio’s character Jack Dawson eventually drowns.

“Well, that was a pretty odd tank… because to break the illusion, it was waist-high at that point,” Winslet said, according to People, describing the filming of the actual scene.

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Kate Winslet described filming the infamous Titanic door scene. (Felix Hörhager/picture alliance via Getty Images)

“So, at first I would periodically ask, ‘Can I go pee for a minute?’ And then I would get up, get off the door, walk to the edge of the tank, about 20 feet away, and literally have to swing my leg over and climb up and walk back to the door. It’s horrible,” she added.

“Anyway, yes. So it was waist high. Leo, I’m afraid to say, was kneeling there,” she added. “I shouldn’t say that anyway. Jimmy Cameron (the film’s director, James Cameron) is going to call me. Actually, the amazing thing about the edges of the pool was that it was an infinity pool. So there was a constant rushing of water and you could hear the constant sound of water.”

Winslet said Leonardo DiCaprio actually knelt in the water during the scene. (20th Century Fox/THA/Shutterstock)

In addition, Winslet recalled the moment she sneaked into a New York theater to watch the film.

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“When the film premiered in London, I was really sick. I had a bad case of food poisoning and was actually in a hospital in London, really weird. And then when the film came out in the US, I was actually at a friend’s funeral,” she said, according to People.

“I mean, it’s horrible to even think about it now. And of course I didn’t want to miss that. So I kind of missed everything around the release of ‘Titanic,’ and I don’t know, is that the universe’s way of protecting me, or is it just to remind me to do the things that are important?”

Kate Winslet stars in the upcoming World War II biopic “Lee.” (Getty Images)

Earlier this year, Winslet also talked about another memorable scene in Titanic.

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Speaking to Vanity Fair about the film’s “I Fly” scene, in which she and DiCaprio stand on the bow of the ship, the actress admitted that the scene looks romantic on screen, but behind the scenes it is anything but romantic.

Kate Winslet told Vanity Fair that the kiss with her “Titanic” co-star Leonardo DiCaprio was “not as great as everyone says.” (Jason Merritt/Getty Images)

“My God, he’s quite a romantic, isn’t he? No wonder every young girl in the world wanted to be kissed by Leonardo DiCaprio,” Winslet said. “It wasn’t as great as it was advertised.”

The Oscar winner described the filming of this scene as “a mess” and attributed the problem to many different factors.

“We kept kissing, and I had a lot of pale makeup on, and I had to check our makeup — both of us, between takes — and I ended up looking like I’d been sucking on a caramel candy bar after every take because his makeup was rubbing off on me,” she recalled. “And he just looked like there was a piece of his face missing because there was this big pale patch of all my makeup rubbing off on him.

“It was a nightmare,” she added. “Leo couldn’t stop laughing and we had to reshoot it about four times because (James Cameron) obviously wanted a very specific light for it and the sunsets were constantly changing where we were.”

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Lori Bashian of Fox News Digital contributed to this report.