With James Cameron hard at work on his new Avatar sequels, producer Jon Landau has revealed the extent to which cast addition Kate Winslet went to pull off her new role.

Cameron, who is currently filming the first and second of the four planned follow-ups, had previously teased that his forthcoming return to the world of Pandora will explore “never before seen parts” which will primarily be set underwater.

Considering this aspect of the next two films – Cameron attributed the sequels’ delay to spending over a year-and-a-half working out how to pull off underwater motion-capture technology – one scene required Winslet to be able to hold her breath for a staggering seven minutes, something the Oscar-winner nailed.

Landau told Collider: “We built a water tank that was 500,000 gallons of water, and we are doing performance-capture under the water, on the surface of the water, and above the water. We trained our cast to free-breath-hold, because in the sequences they have to just be swimming, they can’t be on scuba, and they have to be able to do long takes. So we had a gentleman named Kirk Krack come in and train everybody that needed to be underwater how to go underwater and how to hold their breath.

The most shocking film twists of all time Show all 37 1 /37 The most shocking film twists of all time The most shocking film twists of all time Arrival (2016) The set-up: The services of linguistics professor Louise Banks (Amy Adams) are called upon when aliens arrive on Earth. While experiencing visions of her daughter, who we learn died from cancer in her teens, Louise attempts to communicate with the race in a bid to discern the purpose of their visit. The twist: Louise deciphers the language, which gives her the ability to see into the future. What we thought were flashbacks are, in fact, flash-forwards – her daughter is yet to be born. The most shocking film twists of all time Atonement (2007) The set-up: Briony Tallis (Saoirse Ronan) falsely accuses the housekeeper’s son (James McAvoy) of raping her cousin when she becomes jealous of his relationship with her older sister (Keira Knightley). He’s sent to prison, but is eventually freed to enlist in World War II – and the audience is told that he eventually rekindled his romance with Cecilia and lived happily ever after. The twist: Only, they didn’t. We learn that this is another lie from an older Briony – both Robbie and Cecilia died in the war. The most shocking film twists of all time Chinatown (1974) The set-up: Having been hired by Evelyn Mulwray (Faye Dunaway) to investigate her husband’s death, JJ Gittes (Jack Nicholson) discovers the existence of someone crucial to the case: Evelyn’s sister, Katherine. The twist: After being confronted by Gittes, Evelyn reveals that Katherine is also her daughter – and the result of being raped by her father when she was 15. The most shocking film twists of all time The Crying Game (1992) The set-up: IRA member Fergus (Stephen Rea) promises to protect Dil (Jaye Davidson), the girlfriend of a soldier his group has imprisoned, and soon begins an unexpected relationship with her. The twist: Dil is transgender, and was born male. Fergus's love for her sees him take the fall for a shooting she commits. The most shocking film twists of all time Dark City (1998) The set-up: Having awoken in a bathtub, and discovering he has telekinetic abilities, John Murdoch attempts to find the truth behind a dystopian world that’s inhabited by an evil group who can stop time and implant memories. The twist: His search for meaning sees him reach the end of the city. With nowhere left to go, he breaks through a wall and finds the city is actually an island floating through outer space. The most shocking film twists of all time The Departed (2006) The set-up: Cop Frank Costigan (Leonardo DiCaprio) infiltrates the organisation of gang chief Frank Costello (Jack Nicholson) at the same time that criminal Colin Sullivan (Matt Damon) infiltrates the police force – and both soon suspect they have spies in their midst. The twist: Both end up dead. A shocking sequence sees Sullivan kill Costigan who believes he's got away with it. Sergeant Sean Dignam (Mark Wahlberg) sees to that in an equally as shocking climactic scene. The most shocking film twists of all time Les Diaboliques (1955) The set-up: A woman named Christina is enlisted into murdering her husband by his mistress. However, once the deed is done, his body disappears. The twist: Her husband faked his death with the help of his mistress. The pair wanted to make Christina believe she committed the murder in an attempt to destroy her. The most shocking film twists of all time The Empire Strikes Back (1980) The set-up: Luke Skywalker (Mark Hamill) is trained by Obi Wan Kenobi and Jedi master Yoda to defeat the evil Darth Vader, leading to the showdown of all showdowns. The twist: Skywalker’s delivered a blow after making a pretty huge discovery: the villain is his father. Cue shock and awe. The most shocking film twists of all time Fight Club (1999) The set-up: The world of the film’s insomniac narrator (Edward Norton) collides with that of Tyler Durden (Brad Pitt) as they start an underground club that permits ordinary people to have fistfights with one another. The twist: The narrator and Tyler are dissociated personalties – AKA they are the same person. The most shocking film twists of all time The Game (1997) The set-up: Nicholas Van Orton (Michael Douglas) flees after agreeing to participate in a twisted "game" that sees him – among other things – buried alive and contemplating suicide after accidentally murdering his brother. The twist: It really was just a game the entire time, set up by his brother who wasn't killed at all. The most shocking film twists of all time Get Out (2017) The set-up: Rose (Allison Williams), a white woman, brings her black boyfriend Chris (Daniel Kaluuya) home to meet her family. Chris soon becomes convinced they bury a dark secret and attempts to convince his girlfriend they should leave. The twist: He’s not wrong – only Rose is in on the conspiracy. After uncovering photos of black men she’s had prior relationships with, Chris is abducted, realising that he’s been lured to her cult-like family who want to implant their loved ones’s brains into the body of younger black bodies. The most shocking film twists of all time Gone Girl (2014) The set-up: When Amy Dunne (Rosamund Pike) goes missing, her husband Nick (Ben Affleck) becomes the prime suspect behind her disappearance. The twist: Mid-way through the film, all becomes clear – Amy faked her abduction and spent months framing her husband in revenge for his extra-marital digressions. The most shocking film twists of all time Goodnight Mommy (2014) The set-up: Brothers Elias and Lukas (played by real-life siblings Elias and Lukas Schwarz) believe their mother to be an imposter after she returns home having had her face reconstructed due to a car crash. They take (rather disturbing) matters into their own hands. The twist: One of the twins actually died in the crash. The other, unable to accept his brother's death, has merely imagined him to be alive the whole time and exacts revenge, blaming their mother for his death. The most shocking film twists of all time Identity (2003) The set-up: As a convict awaits execution for several murders, 10 strangers find themselves stranded in a rainstorm at a remote Nevada hotel. Soon, they start getting killed off one by one. The twist: The strangers comprise the split personalities of the convict. The motel is a fabricated reality via which doctors are attempting to find out which one is causing his murderous tendencies. They zone in on limo driver Ed (John Cusack) without realising they've selected the wrong one: the murderous personality is a nine-year-old kid named Timmy. The most shocking film twists of all time Iron Man 3 (2013) The set-up: Tony Stark (Robert Downey Jr) must track down and stop a terrorist known as the Mandarin (Ben Kingsley) who has launched a series of attacks on the world. The twist: He succeeds – but learns that the Mandarin is actually a British actor called Trevor Slattery who has been hired by the actual people responsible. The most shocking film twists of all time Kill List (2011) The set-up: Two contract killers are given a list of people to dispatch of. Their journey leads them to a cult ceremony where one of the men, Jay (Neil Maskell), must kill one final victim known as The Hunchback. The twist: The Hunchback is actually his imprisoned wife with their son strapped to her back. After he kills them, he is crowned by the cultists. The most shocking film twists of all time Memento (2000) The set-up: Leonard (Guy Pearce) is tracking down the man who raped and murdered his wife. However, his search is stunted by his short-term memory loss. Throughout the film, he tells the story of Sammy Jankis, a man who accidentally killed his diabetic wife; she kept requesting more insulin as she didn't believe he had memory loss. The twist: The man responsible only raped his wife and Leonard killed him years ago – he just can't remember it. His wife's actual killer is... himself. His real name? Sammy Jankis. The most shocking film twists of all time Million Dollar Baby (2004) The set-up: A grizzled boxing trainer seeks atonement by helping Hilary Swank's underdog amateur boxer, Maggie, achieve her dream of becoming a professional. The twist: Mid-way through the film, Maggie breaks her neck after being sucker punched during a fight. What was a feel-good underdog story swiftly turns into a hard-hitting drama about euthanasia. The most shocking film twists of all time The Mist (2007) The set-up: Helping several others dodge the monsters lurking in the mist, David Drayton (Thomas Jane) leads the escape from the supermarket they’ve been holed up in. They reach a car and drive away, but soon run out of gas and realise there’s no hope. David loads a gun and, as the camera cuts away, shoots the survivors, including his young son. The twist: As he’s gearing up to put the gun to his own head, shadowy figures roll toward him. He’s devastated to learn it’s actually the military who have combatted the mist creatures. He killed his son for no reason. Talk about awful timing. The most shocking film twists of all time Oldboy (2003) The set-up: Oh Dae-Su (Choi Min-sik) is kidnapped and held in captivity for 15 years. When he's finally released, he exacts revenge with the help of a young girl named Mi-Do (Kang Hye-jung) whom he falls in love with. The twist: The girl is actually his daughter. His captors orchestrated their meeting. The most shocking film twists of all time Orphan (2009) The set-up: The plot centres on a couple who, after the death of their unborn child, adopt a mysterious nine-year-old girl named Esther (Isabelle Furhman) who starts displaying some disturbing behaviour. The twist: Esther is actually a 33-year old murderer who has a condition stunting her physical growth. The most shocking film twists of all time The Others (2001) The set-up: Nicole Kidman stars as Grace, a mother who tries to protect her two children from supernatural forces in their Victorian mansion. The twist: In a spin on the ghost story, it turns out it's Grace and her children who are the ghosts: she killed them – before turning the gun on herself – in despair over the presumed death of her husband in World War II. The most shocking film twists of all time The Prestige (2006) The set-up: The film tracks the rivalry of two magicians, Alfred Borden (Christian Bale) and Rupert Angier (Hugh Jackman), who go to extreme lengths to outsmart one another, each pulling off tricks the other considers impossible. The twist: It emerges that Fallon, the bearded carer of Borden’s children, is actually his twin (he’s also played by Bale) while Angier’s technique is far more disturbing: each night, using Tesla’s technology, he sends his clone plummeting into a water tank. The most shocking film twists of all time Planet of the Apes (1968) The set-up: Three scientists wake up hundreds of years after being launched into space to discover they’ve landed on a planet where primates rule over humans, who are their prisoners. The twist: As Charlton Heston’s character escapes his cell, he eventually finds the Statue of Liberty protruding from sand. Turns out it’s not just any planet – it’s Earth. The most shocking film twists of all time Primal Fear (1996) The set-up: A defence attorney (Richard Gere) has a strong belief that his stuttering altar boy client (Edward Norton) is not guilty of murdering an influential Catholic Archbishop. He's later found not guilty by reason of insanity after being diagnosed with multiple personality disorder. The twist: He faked the disorder. The film's closing moments see him drop the stutter and reveal his guilt as his attorney looks on, disturbed. The most shocking film twists of all time Psycho (1960) The set-up: What viewers initially think is a film about a theft committed by Marion Crane (Janet Leigh) turns out to be something far more darker. On the run, she arrives at a motel owned by Norman Bates (Anthony Perkins) and is swiftly murdered by his mother. The twist: Only, it's not his mother – it’s Norman. He killed his mother years before and has since developed a split personality. The most shocking film twists of all time Saw (2004) The set-up: Having been chained up by the Jigsaw killer in a dilapidated bathroom – which has a corpse lying in the middle of the room – photographer Adam (Leigh Whannell) overpowers and kills his captor. He rummages through his pockets, looking for the key that will unlock the chain around his leg, convinced the nightmare is finally over. The twist: Instead, he finds a cassette recorder that reveals his supposed captor was, in fact, another victim of the Jigsaw killer who was merely following his rules in order to obtain an antidote for a poison in his body. Cue a corpse in the middle of the room rising to reveal himself as the real Jigsaw killer. He was there the whole time. The most shocking film twists of all time Seven (1995) The set-up: David Mills (Brad Pitt) and retired PI William Somerset (Morgan Freeman) have closed in on serial killer, John Doe (Kevin Spacey), who has been using the seven deadly sins as inspiration for his murders. The twist: He has one final murder left to commit – only he’s already committed it. We discover Doe has killed Mills’s wife (Gwyneth Paltrow), which prompts him to complete Doe’s plan by murdering him out of wrath. The most shocking film twists of all time Shutter Island (2010) The set-up: US Marshal Teddy Daniels (Leonardo DiCaprio) and his partner (Mark Ruffalo) arrive at a centre for the criminally insane to find an escaped killer who drowned her three children. The twist: Teddy is actually a patient, and his partner is his doctor. He killed his wife after she murdered their three children and the elaborate ruse is an attempt to bring his repressed memories to the surface. The most shocking film twists of all time The Sixth Sense (1999) The set-up: A young boy who can see dead people encounters a child psychologist named Malcolm Crowe (Bruce Willis) and attempts to discover the reason behind his disturbing ability. The twist: Crowe is, in fact, dead all along. He got killed during a robbery that we see in the film’s opening scene. The most shocking film twists of all time Sleepaway Camp (1983) The set-up: The introverted Angela (Felissa Rose) becomes terrified when a murderer wreaks destruction at the same campsite where her brother Peter was killed eight years before. The twist: Angela is the killer. She's also not Angela at all, but her presumed dead brother Peter, who was raised as a girl by her aunt following Angela's death. The most shocking film twists of all time The Skin I Live In (2011) The set-up: Skilled plastic surgeon Dr Robert Ledgard (Antonio Banderas) tries to develop a new skin that could save the lives of burn victims after his wife, Vera, is burned in an auto accident. The twist: The Vera we're seeing is not wis wife, but a young man whom Robert abducted and subjected to a vaginoplasty six years before. The most shocking film twists of all time Spider-Man: Homecoming (2017) The set-up: Peter Parker (Tom Holland) takes a break from trying to stop the film's villain, the Vulture (Michael Keaton), to go to his school's Homecoming dance. The twist: He shows up to his date's house, knocks on the door... and comes face to face with The Vulture. He's her father. The most shocking film twists of all time Unbreakable (2000) The set-up: David Dunn survives a train crash that kills 130 passengers, and begins to believe he may have special powers. His life soon collides with comic book store owner Elijah (Samuel L Jackson), who has a rare bone disorder, and helps David discover he has the ability to see the criminal acts of those he comes into contact with. The twist: Elijah is the biggest criminal of them all. When David shakes his hand at the end of the film, he sees that “Mr Glass” is the mastermind behind numerous terrorist attacks – including the train crash he survived. The most shocking film twists of all time The Usual Suspects (1995) The set-up: Verbal Kint (Kevin Spacey) reveals a criminal plot concocted by the notorious Keyser Soze. He's eventually set free. The twist He made the whole thing up – Kint is Keyser Soze. The most shocking film twists of all time The Visit (2015) The set-up: A mother’s rift with her parents is healed when she sends her two children, who they’ve never met, to stay with them when she goes on holiday. All is going well until the kids become somewhat weirded out by their strange behaviour. The twist: Their mother becomes disturbed when she sees her parents while Skyping her children - it’s not them. It emerges that these imposters are mental home patients who murdered the couple, and have now taken up residence in their house. The most shocking film twists of all time The Wicker Man (1973) The set-up: A sergeant is sent to a remote island in order to investigate the case of a missing girl. The twist: The girl was never missing – it was just an elaborate hoax to lure an out-of-towner so the island's residents could sacrifice him to their Sun God.

"Kate Winslet had to train in this and she got up to a static breath hold of just about seven minutes. It’s amazing, it’s mind over matter. You see Kate going underwater and she just felt so comfortable. There was one day, we have a tank where she was just rehearsing and testing and we have some windows into it, and I go in there and she’s just walking on the bottom [of the tank] left and right, left and right, left and right, then she sees me in the window and she just waves. I couldn’t believe it."

Having directed The Abyss and Titanic, Cameron is no stranger to water – however, he hinted these sequels could have been his most challenging shoot yet.

“Basically, whenever you add water to any problem, it just gets ten times harder. So, we’ve thrown a lot of horsepower, innovation, imagination and new technology at the problem, and it’s taken us about a year and a half now to work out how we’re going to do it,” he told Collider.

The majority of underwater scenes will take place in the next two Avatar films with the fourth and fifth instalments written and scheduled to be released in 2024 and 2025.

Winslet will appear alongside returning stars Sam Worthington, Sigourney Weaver and Stephen Lang.