The movie was shot in part off the Gold Coast of Australia. Other filming commenced in a giant swimming pool.

Blake Lively was pregnant with her second child during filming.

The crab that Nancy crushes while on her rock is CGI, although the crushed crab she attempts to eat is real. Blake Lively's reactions of disgust are genuine as Director Jaume Collet-Serra states "we're not allowed to harm any animal, so there were no live crabs, but we did send our art department out in the mornings to go find crabs that had died naturally on the beaches, so there's a couple of those in there."

Steven Seagull's name in real life is Sully. He lives (to this day) in a seagull sanctuary in Australia. Two extra seagulls were used to portray Steven Seagull. According to producer Matti Leshem, she added "They were all good but not nearly as good as him. Peggy was the vocal one, the very squawky bird. Gaviota (which means seagull in Spanish), I think he's almost 30 [as Steven is estimated to be about 15 or 20 years old]. The most challenging thing about Sully as an actor is that seagulls are remarkably clean. They self clean a lot, so the blood on Sully, obviously fake blood, he kept wanting to clean it off, so we had to deal with that."

Jaume Collet-Serra teamed up with the art department for the design of the shark. "I came to the conclusion that the shark had to be female", says the director. "Females are slightly bigger and have great scars from mating. Visually they're scarier, as they are more protective." Creating the shark generally took thousands of hours of research, so the film crew watched every Shark Week episode to get the idea of creating the shark he further added "she's a female shark, we know exactly how much she weighs. Every scar that she has has a story behind it. It's really an incredible job of artistry and research".

Blake Lively was partly inspired by her husband Ryan Reynolds work in the similarly minimalist film Buried - Lebend begraben (2010), stating "that was one of the reasons why I wanted to take on this movie so much, because I know how tough that was for him and how rewarding it was."

Blake Lively only had a stunt double for the surfing scenes as she couldn't surf professionally, "All I did was paddle" she recalled, her surfing stunt double was professional Australian Surfer 19 year old Isabella Nichols, she taught Blake how to paddle correctly, how to wax a board and put a leg rope on and fins in to make it look authentic.

Blake Lively revealed in an interview that she is terrified of sharks in real life and that she never saw Der weiße Hai (1975).

The movie was originally going to be filmed on the Gulf Coast of Texas near Galveston but the filmmakers were denied a film permit for safety reasons.

The screenplay for this film was featured in the 2014 Blacklist, a list of the "most liked" unmade scripts of the year.

Director Jaume Collet-Serra viewed the movie as one about survival and decided not to place an emphasis on gore and noted "This isn't a creature movie."

Much of the film was shot in a tank with bluescreens for effects, still Director Jaume Collet-Serra wanted to avoid the "more stylized look" of similar films using the set-up and estimated that 10% of the film was shot on location in order to "trick" the audience into believing the setting was real. He explains "every scene has one shot that is real and the other 99% is not-but the one real shot tricks you".

For the seagull character of Steven Seagull, the usage of both CGI and a puppet was considered based on the belief that it would be inordinately hard to train such a bird to act. This "horrified" both producers, Matti Leshem and Lynn Harris, who wanted to use an actual seagull while scouting for location in Australia. Blake Lively was able to feed a group of seagulls, at which point it was realized that using such a bird would be possible.

The dead whale was a mix of CGI and a styrofoam prop.

The initial script featured Blake Lively talking to the seagull much more and likewise scenes featuring such an interaction were shot; however, in the end Director Jaume Collet-Serra decided on a less-is-more approach, noting to Yahoo that "...we didn't want her to be like Snow White talking to animals; when you see her predicament you get it, you don't need her to explain everything to a Seagull!"

The movie was originally titled "In the Deep."

For Blake Lively surfing some digital effects were used to take on the waves,the production company utilize face replacement techniques orchestrared by Lola VFX (Famous for its face replacement work on The Social Network (2010) and The Return of the First Avenger (2014) Anderson stated " they have their own proprietary methodology for doing the face work, but they realized pretty quickly that surfing shots are full of their own challenges, they scanned Blake and got performances of her with their rigs and setups then had to transfer that to a 3D version of Blake's face that is tracked, reanimated and replaces the stunt doubles face"

Blake Lively revealed in an interview during principal photography "The most difficult part about it was having to wear a vest to make the location look more tropical but really it was freezing, but I wasn't complaining because the waves were pumping!"

The sheer size of the shark made a great difference to the animators, Scott E. Anderson told the animators to "think of the shark as a big diesel truck with lots of power and torque, versus a high-revving German engineered car." Anderson continues, "it's big and sleek with a graceful, powerful way of swimming, we use that mass when she's attacking the buoy or hitting anything else- she's got a huge heavy size to her".

Blake Lively's hair stylist, Rod Ortega, had to get into the tank to do Blake's hair, Blake recalls: "He basically spent 30 days in the tank with me-like in the water the entire time he was doing my hair from the water he was like a fish."

The film crew had to ride bikes to the set every morning. Producer Mattie Leshem added "We weren't allowed to have too many vehicles on the island, so essentially everyone had to ride their bikes to set every morning. But because we needed all the daylight to shoot in, we were riding in the dark. And in order to get close to the set, we had to get off our bikes and walk to the beach, because there is a Muttonbird population and it's an endangered species and 20,000 of them were nesting exactly at the time we were shooting the movie. And they're incredibly fast in the wind but when they're on the ground, they're like drunken ducks so if you're riding a bike you could easily run them over. We were warned under no circumstance could we hurt a single Muttonbird and [we didn't]."

The digital shark was mostly done by a Swedish company that is a digital shark specialist called Important Looking Pirates (ILP). Ever since their groundbreaking sharks and water simulations on Joachim Rønning and Espen Sandbergs Kon-Tiki (2012).

Blake Lively said in an interview during principal photography about doing her own stunts that "there wasn't a single scene that wasn't stunt-heavy, doing the underwater sequences I'm in 4.5 foot waves" she shares describing her toughest days on set "whether I was in the tank or when I was in the ocean I was about 300 yards away from Shore they would drop me off on this rock that was three feet by three feet, you're in the wild, you are in the land of big, incredible, majestic wild creature and if you're wearing a wetsuit you're dressed as a seal".

Blake Lively came up with the name "Steven Seagull." Producer Matti Leshem noted "she really made her own relationship with Sully. There's a moment in the film where she's fixing his broken wing and the bird really bit her. I would say that relationship was complex in the sense that there was a lot of love there and they really bonded, but there were moments that you could see Sully really lashing out. Obviously she was trying to help him, but I think the complexity and deep emotional bond that they have between them is what makes this movie great."

The movie was filmed in 47 days, with principal photography from October 28th to December 13th 2015.

This movie marked Blake Lively's second star (not co-starring) billing. Für immer Adaline (2015) was her first.

Blake Lively's orange bikini was a gift from fashion designer Tory Burch.

Due to unexpected box-office success, whether a follow up sequel was possible, film director Jaume Collet-Sera said in an interview he doesn't believe in sequels, he can only do original work. Which is an ironic statement considering he started his directorial career with a remake (House of Wax) and a sequel (Goal II: Living the Dream).

Louis Leterrier was originally set to direct but exited the film, due to creative differences and the reduction of previously told budget.

For all the obvious reasons, the film's great white shark was created digitally. Great whites generally do not survive well in captivity, Slashfilm has noted that the use of CGI was unusual for the director, as he typically uses practical effects as opposed to digital ones required by the shoot.

The shark had multiple personalities, although one digital shark became the main adversary to Blake Lively the filmmakers deliberately crafted a few different shark "stages" VFX supervisor Anderson explained it began with "The early naturalistic shark, representing the fact that Nancy just wandered into a sharks feeding situation before becoming a more directed shark during the buoy sequence and leading into the more directed and stylized action of the flare sequence, culminating with Nancy in the water and finale with the shark, through it all footage of real sharks were used to give use that sense of balance from the simplicity of a fin through the water s-curve of a shark swim, the gills reactions, the motion of the 'lips' and an overall sense of mass. This was all driven by reality, but controlled by animators following Jaumes desires for each scene".

14 visual effects Studios were involved including important looking Pirates, Digital Sandbox (DSBX), Scanline, MPC, Lola VFX, Spin, Aaron Kupferman studios, Mammal Studios.

The VFX crew also provided a slightly different look two underwater views versus the shark above the water VFX Anderson stated " the underwater look of the shark had a particularly aesthetic that was really driven by Jaume and his scene by scene mood of the film, we started with very realistic looks and actions culled from a large amount of shark reference footage, that drove both the look development and character development at ILP, what was this actual difference? Underwater we did tend to keep the shark a bit more shiny than it is in stock footage it just made our hero shark more of a star than the flat look of unlit footage. We were also balancing the look between visibility and naturalistic blending of the shark into the environment. Most animal, sharks included are designed to blend into the environment our job is to use visibility selectivity to meet the needs and direct the audience and eye when we want our need to".

Nancy's nickname for the seagull is Steven Seagull, which is, of course, a pun on actor Steven Seagal.

Blake Lively wears a Baby-G BG169R-8 model gshock. However, that model doesn't feature a tide graph in real life.

Director Jaume Collet-Sera said that script was re-tailored to fit Blake Lively, as the original character was a younger one, about three to four years younger.

In the beginning of the movie, the two surfers ask Nancy (Blake Lively) if she is from California and she says she is from Texas. In real life, Blake Lively is from California.

Carlos (Óscar Jaenada) drives a 1997 Jeep Wrangler [TJ].

Blake Lively was born the same year a month after the shark movie, Jaws: the Revenge (1987) came out during the summer.

The shark meets its doom after being impaled on a rebar at the bottom of the sea floor. Live-action tank footage of actress Blake Lively was combined with the final CG shark and sea-floor crashing effects.

Blake Lively slammed her face into the buoy, which caused her a running bloody nose while shooting the climactic ending. The blow to the face and bloody nose both made it into the final cut of the film, which can be seen during the ending climax.

In creating the shark, director Jaume Collet-Serra wanted to create a worthy adversary that would keep the audience on the edge of their seats. "I wanted the shark to be a presence for half the movie," Collet-Serra said. "I wanted to reveal it slowly, then have it to be a force of nature; my reasoning was that if Nancy doesn't get a good look at the shark, then the audience shouldn't get a good look at it either".

Blake Lively shot the jellyfish scene, in which her character is surrounded by hundreds of jellyfish, in pitch black water, director Jaume Collet-Serra noted "she was in a tank that was completely blacked out, the cinematographer and I had these lights that were underwater just underwater bulbs and they're essentially where the CGI jellyfish are, she was willing to get into a pitch dark tank and get underwater, she also had an uncanny ability to hold her breath, I think she was holding her breath beyond a minute she's like a superwoman".

The shark has only 4 minutes of screen time.

In animating the shark, Anderson's greatest challenge was to create a believable character. "The shark is very consistent in its character", he says. "Nancy wanders into its area accidentally and interrupts the shark's world, and after the shark has wounded her, the shark just thinks of Nancy as food. It's nothing personal - the shark is just being a shark. Towards the end when Nancy is fighting for her own survival, the shark fights back; both of them are just doing what they need to do."

At the end when they are in "Galveston", the Gulf of Mexico's water is shown to be a clear blue. The water off of Galveston's beaches are usually muddy brown but can be clear blue during the summer.

Nancy finds her strength and courage and makes her stand for survival on the buoy which is number "42". 42 is considered, in pop culture, to be the answer to the meaning of life. As in the famous Douglas Adams book Hitchhikers Guide To The Galaxy where 42 is the answer to the ultimate question.

The name of the beach is never revealed. It may have been Isla de tiburón (shark's island).

Nancy uses a Webley & Scott No. 2 Mk. V Signal Pistol against the shark at the end.

Body count: 3.