2003’s Open Water shark movie is based on actual events surrounding the disappearance of an American couple scuba diving in the shark-infested waters around the Great Barrier Reef off the coast of Queensland, Australia. The movie was written and directed by Chris Kentis, and produced by Kentis’ wife Laura Lau — both avid divers. The couple shot the film over the span of two years, and they funded the project with $130,000 of their own money. The movie became a sleeper hit, upended the Killer Shark genre, and went on to earn over $54 million worldwide.

The Open Water shark movie tells the terrifying story of a couple, Daniel Kintner (Daniel Travis) and Susan Watkins (Blanchard Ryan), who go on a diving expedition and find themselves stranded 20 miles offshore. What makes Open Water a different type of killer shark movie than say, The Meg franchise or Deep Blue Sea, is that it’s based on a harrowing true tale — albeit with a few necessary tweaks to make it work for the big screen. The film was so successful that an initially unrelated movie was retooled during production to become the Open Water sequel, Open Water 2: Adrift.

Open Water Is Based On Tom & Eileen Lonergan Scuba Diving Mishap

Tom & Eileen were accidentally left behind while scuba diving on vacation

Open Water focuses on fictional holidaymakers Daniel and Susan, but their story is based on a real-life tragedy that befell Tom and Eileen Lonergan. During a vacation at an undisclosed location in the Open Water shark movie, Susan and Daniel embark on a scuba diving trip and stray from the group. They resurface to discover the tour boat has left them behind after a member of the crew performs an inaccurate headcount. At first, the couple believes their absence will be noticed, but as the hours wear on, their situation’s harsh reality begins to sink in. Unfortunately, this nightmare scenario is one possibility for what happened to Tom and Eileen Lonergan.

Of course, Open Water does embellish some details since exactly what happened to the Lonergans still isn’t known. The Open Water movie’s most frightening moments are derived from the presence of multiple numbers of sharks that Susan and Daniel are powerless to fend off. Eventually, Daniel is bitten, and at some point during the night, he dies either of blood loss or shock. Susan releases Daniel and watches his body get ravaged by the predators. Realizing she’s going to die, Susan removes her gear and sinks beneath the surface. However, while it’s possible Tom and Eileen Lonergan met their end at the hands of multiple sharks, the true Open Water story is actually part of a mystery.

Open Water Is Also Based On A Novel

The sequel was a short story adaptation

Unlike the Open Water shark movie that was inspired by real events, the 2006 sequel Open Water 2: Adrift is an adaptation of a short story — a story that isn’t at all connected to the disappearance of Tom and Eileen Lonergan. Since the second Open Water movie was marketed with the tagline “BASED ON TRUE EVENTS”, many viewers believed it was also derived from a real-life case of a shark attack like the first Open Water. The short story that inspired Open Water 2: Adrift is entirely fictional though.

The “true events” behind the second Open Water were written by Japanese author Koji Suzuki, the author of the novel adapted into 1991’s The Ring (Ringu). The short story, Adrift, was part of the 1996 collection Dark Water, which also contained the short story eventually adapted into the 2005 movie of the same name. Interestingly, Open Water 2: Adrift was originally intended to be a straightforward adaptation of the Koji Suzkui story entirely unrelated to the first Open Water movie. It was thanks to Open Water’s success that the follow-up became attached as part of the same franchise, as this was the only way studios would option the story.

Were The Real Tom & Eileen Lonergan Attacked By Sharks? The Couple’s Deaths Explained

Their specific cause of death is a matter of speculation

In the weeks following the couple’s disappearance, pieces of their scuba equipment washed up on a deserted beach, and while there was damage, it was attributed to coral and not an animal attack.

Tom and Eileen Lonergan disappeared in January 1998 during an expedition run by Outer Edge Dive to the rim of the Great Barrier Reef 40 miles offshore Port Douglas, Queensland. As in the movie, Tom and Eileen went off on their own and resurfaced late. It took two days for the boat’s skipper to report the couple’s disappearance — in the film, the incident is reported the next morning — leading to a week-long search, but their bodies were never found. In the weeks following the couple’s disappearance, pieces of their scuba equipment washed up on a deserted beach, and while there was damage, it was attributed to coral and not an animal attack.

According to a 2004 article in the New York Times, some people believed the Lonergan’s faked their deaths, a conspiracy theory authorities debunked. Journals found among the Lonergan’s personal belongings painted Tom as a man with a “death wish.” This led to speculation that Tom may have killed Eileen and then himself. Eileen’s father, John Hains, believes Tom and Eileen became dehydrated and disoriented, which would have led them to shed their suits and equipment, resulting in death by drowning or sharks. While there’s no way of knowing with certainty what happened to Tom and Eileen Lonergan, the mystery was more than enough to be the real events that inspired Open Water.

Why It Took The Boat Crew So Long To Discover Tom & Eileen Lonergan Were Missing

The diving crew’s negligence led to the Lonergan’s deaths

Remarkably, nobody on the boat, including the passengers or the crew, pointed out that Tom and Eileen were missing when the boat departed and essentially left them for dead. It took two days for the incident to be reported to authorities, which was another glaring misstep and act of negligence on the part of the diving staff. Those two days could have been the difference between life and death for Tom and Eileen. There was no clear explanation ever given by the diving crew about how they could have been so incompetent and forgotten that two of their customers went missing.

How Tom & Eileen Lonergan’s Disappearance & Deaths Changed Diving In Australia

New safety protocols were immediately enforced

As a result of the tragedy of Tom and Eileen’s disappearance and presumed deaths, stricter regulations were put in place for the diving industry of Queensland. Of course, the biggest result of their tragedy was the 2003 movie Open Water, which has become an iconic staple of the killer shark genre ever since it was released in theaters. The film received a Certified Fresh rating on Rotten Tomatoes with a score of 71% and at the very least gave Tom and Eileen’s story a platform even if its primary intention was for entertainment purposes. Open Water is a sharp reminder that even some of the most terrifying movies can be based on real-life experiences.