Keira Knightley knows a thing or two about boat-related movies. But as it turns out, filming on a $150 million superyacht for The Woman in Cabin 10 was a lot more difficult than filming on a pirate ship.

“You can break the pirate ship,” Knightley explained in a recent Zoom interview with Decider. “Whereas this it’s like, ‘Okay, run because somebody is trying to kill you—but don’t touch the walls!’ It was a particular challenge not breaking anything, and knowing that if you did break something, you’d get a bill for like 200,000 grand.”

The 40-year-old Oscar-nominated actor—who became a global superstar at 18 for her role as Elizabeth Swann in the Pirates of the Caribbean franchise—gets back out on the water in this new Netflix thriller, which began streaming today. Based on the 2016 novel by Ruth Ware, The Woman in Cabin 10 stars Knightley as an investigative journalist named Lo, assigned to cover what she thinks will be a fluff piece on a luxury cruise for charity, hosted by a wealthy businessman (Guy Pearce). After she witnesses a passenger thrown overboard, only to be told she’s crazy, Lo uncovers a dark conspiracy.

The film was directed by Australian filmmaker Simon Stone (who also directed the 2021 Netflix film The Dig), who was proud to report to Decider that no, he didn’t damage the $150 million superyacht. Mostly.

“I think we scratched a little bit of the floor, and had to spend a grand on buffing one section of floor,” Stone admitted to Decider. “But that was pretty good.”

Knightley and Stone spoke to Decider about the difficulties of filming on a pricey boat, spending fall in the English Channel, and Knightley’s too-good swimming technique.

DECIDER: I want to start with a question for both of you, about filming on that expensive superyacht. Were you guys out on a body of water while filming on the boat?

KEIRA KNIGHTLEY: We were in the English Channel. It was cold! Unsurprisingly, for the English Channel, really.

SIMON STONE: That’s right. I think a lot of the actors who I was meeting with for the film, were like, “Oh, great, we get to be on a superyacht! So where are we shooting?” And I’d be like, “Oh, the coast of the south of England in fall.” And then you see the face drop of like, “Oh, this is going to be miserable.”

KK: This is going to be a lot of rain, and really cold, and windy, and hard!

SS: But that all looks great on film, if you’re making a Scandi-noir thriller. Those are the perks. You sit outside and you go, “Wow, that looks scary and intense.” I don’t think any of us would compare what we do to, you know, Médecins Sans Frontières [Doctors Without Borders].

KK: No, we definitely wouldn’t!

SS: [Laughs.] It’s not like our job is hard. But shooting on a superyacht, ironically, is not luxurious.

KK: The yachts are built for 25 crew and 12 guests. We had the 25 crew, and then we had 70 film crew, and then we had 20 actors. We weren’t allowed to touch anything. We weren’t allowed to sit on anything. We weren’t allowed to like, walk on the carpet. So we were all just kind of crammed in the middle. We weren’t allowed to eat or drink anything, apart from in tiny little designated areas. It was not quite your image of what your experience of being on a luxury super-yacht might be.

I read that you guys had to keep switching shoes. Did you add that detail for Lo’s character about being asked to take her shoes off after that happened to you?

SS: Yeah, of course! I mean, it didn’t actually happen to me, because someone had warned me before. But I was like, imagine if you weren’t warned. It’s the moments where you create empathy. For all the klutzes in the world, speaking as one of them, it is great to have a little moment of, “I like her because she does the wrong thing.” She didn’t realize that the dress code is actually dressing down if you’re rich, as opposed to dressing up. That makes her incredibly likable because we all go, “That would totally be me in that situation.”

Keira, I’d say you’ve spent more of your career on boat-related scenes than the average movie star.

KK: I think so, yeah!

Would you say that filming on a superyacht is more or less challenging than a pirate ship?

KK: The pirate ship is easier, because you can break the pirate ship. Nobody is telling you not to sit or lean or walk or stand. You can run around, and you can do the thing. Whereas this it’s like, “Okay, run because somebody is trying to kill you—but don’t touch the walls!” It was a particular challenge not breaking anything, and knowing that if you did break something, you’d get a bill for like 200,000 grand.

Did you guys break anything?

KK: No, no, we were terrified!

SS: I think we scratched a little bit of the floor, and had to spend a grand on buffing one section of floor. But that was pretty good. We did well. We were well-behaved.

Tell me about filming that harrowing scene where Lo jumps overboard and swims to shore. Keira, your freestyle is very impressive, and you’re wearing a sweater, no less!

KK: I was in a tank. I think that was between me and my amazing stunt double, Jess [Jessica Hooker], who actually did all of the cold water stuff.

SS: All the freestyle is you! You’re in the tank, but it’s all the underwater stuff that we use. You’ve got good technique. I had to keep telling her that she had to be more exhausted, and also more in shock. She was she was really, really impressive. Even in the edit, after I’d given her the note several times—”You need to be shitter at swimming”—I then, had to find the few brief moments-

KK: Where I looked crap at swimming?

SS: No, you have good technique, but then you’re then you’re really tired, in some of them. Because we need to be worried that you’re going to die, obviously.And in some of the shots, it was like—that’s Bear Grylls!

Keira, my last question for you—I saw you’re voicing Professor Umbridge in the new Harry Potter audiobooks. Are you aware that some fans are calling for a Harry Potter boycott, given J.K. Rowling’s ongoing campaign against trans people?

KK: I was not aware of that, no. I’m very sorry. You know, I think we’re all living in a period of time right now where we’re all going to have to figure out how to live together, aren’t we? And we’ve all got very different opinions. I hope that we can all find respect.

SS: I think that’s right. I think that we have learned over time, unfortunately, that the unbearable voice in the room is something that we should try and shut down. And actually, I think everyone needs to recognize that they’re the unbearable voice for someone else, as well. The live and let live thing of like, “Oh God, your voice is really loud, and I can’t stand you.” That’s part of our lives.

We all have hatred, deep hatred for someone in the universe—someone in the class. Let’s reduce it to classroom politics. There is always the kid that we cannot stand. I think we’d all agree that where that kid for someone else, too. Unfortunately, all sides of the political spectrum are currently trying to shut that kid’s voice down, but they don’t realize the irony of the fact that they’re also that kid for someone else. If we can have all have a moratorium on that, and just let chaos live for a little bit, we might find our way out.