Actress Frances Fisher Reveals 'Nobody Could Breathe Correctly' on Titanic Set Due to the Corsets

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Frances Fisher is getting candid about the challenges that came with her Titanic costumes.

The Sinner actress, 70, who did a Q&A with Vulture about the movie — which celebrates its 25th anniversary Monday — gave some insight into how it felt donning the tight corsets and heavy hats to play Ruth DeWitt Bukater in the period piece.

"It was the easiest role to ever get into, because Deborah Scott, the magnificent costume designer, dressed us from the inside out," Fisher said. "Having that corset on completely changes your breathing style and posture. ... Nobody could breathe correctly."

"Also the hairstyles," she continued. "That was all my hair put up under a huge hat. That was another thing that contributes to a kind of grumpiness that I think Ruth had."

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Fisher said it was difficult for some of the actresses to sit down and rest between takes because their costumes were so constricting, and their hats also prevented it.

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"The corset would dig into your body, and you couldn't lean back — the hat was so big. They had all these resting boards for us, but nobody who had their hair up in a big hat could use them. The proportions were incorrect," she explained.

She and the other ladies would opt to "stay upright" while they waited to shoot their scenes.

The actress also noted that going to the bathroom on set in costume was a whole other challenge in itself, but she and her female costars figured out a way.

"When we were shooting on the ship, some of the women — like Kathy [Bates], Kate [Winslet], and I — would say, 'Okay, are you guys ready to go back to the dressing room to relieve ourselves?' " she recalled.

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"They had porta-potties on the set, and there was no way any of us could get into a porta-potty with those big dresses on," she explained. "So we would stand in the back of a flatbed truck, and they would drive us back to the dressing rooms, so we could take care of what we needed to take care of."

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Titanic went on to become the first movie to reach $1 billion at the theaters, and still holds a special place for some of the actors, as well as director James Cameron.

In an exclusive interview for PEOPLE's new Titanic special edition issue Cameron said he kept going with his research on the RMS Titanic, even after the movie premiered. He even returned to the wreck site for several documentaries, notably 2003's Ghosts of the Abyss and for a planned National Geographic documentary set to premiere in 2023.

"Yeah, I was a little bit obsessed there for a while," Cameron told PEOPLE. For now, he added, "I'm not going back out to the wreck. I've done my investigation. We are putting all our data together with some of the other experts . . . to do a definitive publication on the marine forensics of the wreck."

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He also revealed to Deadline that the studio behind the film originally didn't want Leonardo DiCaprio as its star, and he had to fight for him to be in Titanic. He noted that he didn't think the film would have been as successful if it all didn't come together the way it did.

"You think at any one of those places, if that had really kind of frayed apart, it would have been somebody else and it wouldn't have been that film," he told the outlet. "And I can't imagine that film without him and without her."

"So there's a fragility to the whole process, there's a fragility to success," Cameron added. "You change one element and it doesn't work."