[6][7] In 1992, a young girl, Rebecca Summers, goes out to her family pool one night to retrieve a toy boat belonging to her terminally ill brother, Tommy.

In the present day, the Waller family—Ray, Eve, and children Izzy and Elliot—are seeking a new, permanent residence after Ray has been forced to retire from his baseball career due to multiple sclerosis.

Eve returns to the house to find that Ray is being directly controlled by the entity, which traps Elliot in the pool and attempts to kill Izzy.

Deciding to remain in the house so that no one else falls victim to the entity, Eve, Izzy and Elliot make arrangements for the pool to be filled in to stop such a thing happening again.

Judson Scott, executive vice president at Atomic Monster, recommended the short to James Wan, who agreed to purchase the rights for a feature film adaptation.

Wyatt Russell and Kerry Condon were announced to star, with James Wan and Jason Blum producing under their banners, Atomic Monster and Blumhouse Productions, respectively.

In order to intensify the supernatural feel, McGuire and cinematographer Charlie Sarroff used older and wider lenses to make the pool seem as vast as the ocean.

Everything from keeping the water clear enough to have visibility and having the right flashlights to the amount of time talent could safely hold their breath required specific problem-solving and strategies that you'd never even think about until you're making a movie called Night Swim".

To reflect the film's influences, McGuire incorporated pop songs from the 1980s to the soundtrack, such as having the character of Ray Waller have a thing for 80s metal to have him feel like he's drawn to the past.

The website's consensus reads: "Despite a promising start and a handful of solid scares, Night Swim is undone by a premise that just isn't strong enough to support a feature-length film.

[21] Frank Scheck of The Hollywood Reporter called the film "the shallow end of the horror-film pool" and said "despite the filmmaker's best efforts to drum up suspense via the usual jump scares, Night Swim turns out to be just as silly as it sounds".

[22] Toronto Star's Peter Howell gave a score of two out of four, saying the short story was superior: "For the most part, though, this feature version of Night Swim further demonstrates the truism that longer is rarely better when it comes to movies.

[23] Matthew Monagle, writing for The Austin Chronicle, gave the film a score of three out of five: "It may be damning with faint praise to describe Night Swim as a solid movie, but horror fans know just how dark and deep the bottoms of their genre can be.

She wrote that the third act's goofiness undermined the "emotional resonance it's going for", but ended the review with, "For a winter horror release — typically a great time to go to the movie theater, munch popcorn and get your pants scared off — it does the job".