At the depth the characters are, experts suggest there would be less than 15 minutes of air for them.
To replicate the organisms found underwater, finely chopped broccoli was added to the tank. Mandy Moore said it was quite unpleasant after a few weeks. She even compared it to filming inside a soup.
Like many shark movies, 47 Meters Down portrays its sharks in a slightly exaggerated way, i.e. with more aggression. But Outpost worked with the director to retain as much of the 'classic' aspects of shark behavior as possible while still creating the feeling of terror and panic for a horror film. Says Kolendo: "We looked at how the jaws behave when a shark attacks, what the gills are doing when it turns in anger, how fast is the tail moving to propel the massive body, and then we added that extra few percent to exaggerate the action, creating a shark that is not only believable, but also terrifying."
James Van Der Beek was cast as Lisa's boyfriend Stuart, and filmed several scenes with Mandy Moore. However, all of those scenes were cut. The final version of the film only references Stuart.