This so-bad-it's-good shark flick swam into theaters on July 28, 1999. Here are a few things you might not have known about it.

1. Deep Blue Sea was inspired by a macabre experience.

When he was growing up in Australia, Deep Blue Sea screenwriter Duncan Kennedy saw the remains of a shark attack victim, which had washed up near his home. "There was really not much left of him," Kennedy told the Los Angeles Times. Kennedy had nightmares about being trapped in a passageway with sharks that could read his mind, and channeled those dreams—and his childhood experience—into the script about sharks whose brains have been modified by a scientist conducting Alzheimer’s research, making them smarter and much more deadly.

2. Many of the sharks in the film are real.

Most of Deep Blue Sea was shot at Baja Studios in Mexico, where the team constructed sets above the massive tanks that James Cameron built to make Titanic. There, the cast worked with animatronic sharks and used their imaginations to sub in for CG sharks that would be filled in later. But after the shoot at Baja wrapped, director Renny Harlin insisted that the cast head to the Bahamas to shoot with real sharks. Thomas Jane, who played shark wrangler Carter, was not thrilled: “I’ve been scared of sharks all my life, ever since I saw Jaws," Jane said in a DVD special feature.

Jane later recounted the experience for Entertainment Weekly: "The first day, I was in a cage, but the next day, they swam me 30 feet down ... Then this guy yanks the breather off me and the water's churning with blood and guts and stuff ... It was so terrifying that I don't want to remember it."

3. director Renny Harlin made tweaks to the sharks to take on Jaws.

"The problem with approaching a shark movie," Kennedy told the Los Angeles Times, "is how do you do it without repeating Jaws?" Kennedy said that in order to “do Spielberg one better,” Harlin made Deep Blue Sea’s makos 26 feet long. In real life, shortfin mako sharks reach 10 feet on average (although specimens as large as 12 feet have been caught), and longfin makos reach as long as 13.7 feet.

4. The animatronic sharks were really believable.

Deep Blue Sea’s filmmakers created its monstrous makos with a combination of visual effects and animatronic sharks. “My whole approach to this movie was, no more hiding sharks,” Harlin said in DVD special features. "This time you’re going to really see them. That’s a challenge. We’ve seen sharks on the Discovery Channel. We know what they look like, so our sharks had to be totally convincing.”

The special effects team, headed by Walt Conti—who built Willy in Free Willy and the snakes in Anaconda—spent eight months on the animatronic sharks. “The number one thing about capturing sharks is getting their energy,” Conti said in the film’s production notes. “They're always cruising kind of slowly, then they snap and just go with this incredible burst of energy. In that way, most of the time, sharks are somewhat lethargic. So probably our biggest challenge was replicating that speed and energy for those lunges. Also, sharks' jaws actually float in their skulls, giving them a specific kind of motion. As far as I know, we're the first animatronics team to totally mimic the multifaceted jaw of the shark.”

To get the job done, the team watched video of real makos swimming frame by frame, then borrowed equipment and technology that’s typically used in 747s and built the sharks as self-contained units. The remote-controlled machines had 1000hp engines, weighed 8000 pounds, and swam on their own, without the use of external wires or apparatus, at up to 30mph. They built 4.5 sharks: Three 15-foot makos, which played the first gen sharks; and 1.5 generation-two sharks, which represented that first generation’s 26-foot-long progeny. The effect was quite realistic: “The first time I saw one of those animatronic sharks, I thought it was a real one,” Stellan Skarsgård, who played Jim Whitlock, said in a special feature created for the DVD.

“When they first brought [the animatronic shark] into the lab we were all in awe of the size of this machine,” Jackson said. “It was a real monster. I would walk up to it slowly and touch it and they said it felt like a real shark. The gills moved and it had a mind of its own sometimes.”

Harlin recounted one of those times in the DVD commentary. “[One shark] was sitting in [McAlester’s] room and just as we were getting the computer programming finished, all of a sudden it leapt up [and] went through the ceiling,” he said. “All these 2x4s flying away like matchsticks. It was a good warning for us. It gave us an idea of the awesome power of these creatures and how careful we had to be in terms of the cast and crew being close to them, and how the computer program had to have failsafe procedures so nobody got hurt.”

5. Samuel L. Jackson was originally offered a different role.

In the original script, there were two men in the kitchen; Harlin initially thought Jackson would play Preacher, the head chef. But Jackson turned it down, “because my agent didn’t like it or the part wasn’t big enough or something,” the Oscar-nominated actor said in DVD commentary. So Harlin cast LL Cool J as Preacher and came up with a different part for Jackson.

“He said, ‘Now you’re going to be the richest man in the world, and you’re going to have the greatest scene in the movie, and it’s going to be a shock to everyone!” Jackson recalled. “He sent it back, [and the part] was Russell Franklin, and I was like ‘Yeah, this was great.’ I’ve done a lot of different things in movies, or had a lot of things happen to me in the movies, but nothing like what happens to me in this one.” (More on this later.)

Jackson told the Las Vegas Sun that he was motivated to take the part because “I watched a lot of monster pictures growing up and we would go home and someone would pretend to be Dracula or Frankenstein and chase us and we would run from them. This was an opportunity to finally be in a movie like that and run away from something that's bigger and stronger, with sharp teeth and claws. I got to say stuff like ‘Look out, look out! Go this way! Ahhh! Ahhh!’ Even though I didn't get to be that panicky.”

6. If you pay close attention, you'll see a special nod to Jaws.

In the beginning of the film, shark wrangler Carter, played by Thomas Jane, removes a license plate from the teeth of a tiger shark, then gives it to Russell Franklin. Take a closer look, and you’ll notice that it’s the exact same license plate taken from the stomach of the tiger shark that’s cut open in Jaws. Harlin called it “a little nod to the grand master, Spielberg.”

7. Harlin makes a cameo—and he was not a natural.

Carlos Alvarez, Getty Images

As the workers of Aquatica—the lab where the research takes place—are heading home for the weekend, you can see Harlin walking past. “I had a moment of temp insanity—a friend of mine was visiting the set and we decided to walk through the scene,” he said in DVD commentary. “It took 20 takes to get me just walking through it without walking into the other actors or falling off the dock. There’s a reason why some people should stay behind camera.”

8. An accident made it into the finished film.

According to Jackson, working in the water so much wasn’t just unpleasant—it actually led to an accident that made it into the final film. “When we get Stellan [Skarsgård] hooked up to the helicopter and we're trying to get back to the elevator during the storm, the waves are supposed to rush in front of us and behind us,” Jackson recounted. “At one point three tons of water got thrown on us by accident and we got swept toward those cargo bays and everyone thought we were going into the drink and people were tumbling around this metal grating ... We scrambled up and kept acting ... Everyone was kind of [upset] because they hit us full on with three tons of water. That was not supposed to happen and we didn't have safety harnesses on and we were flailing around on this deck.” Still, Jackson said, “I thought that was pretty funny when I saw it in the final film. I said, ‘Oh, they kept that.’”

9. The parrot was not a professional.

There wasn’t a huge budget on the movie, and in DVD commentary, Harlin said that there was “lots of discussion about should we have the parrot, should we not have the parrot” for LL Cool J’s character, Preacher. They opted to have the bird, but, Harlin said, “we couldn’t afford a Hollywood parrot—a parrot that is fully trained and comes with its professional trainers and does tricks and speaks on cue and so on. So we decided to go with a parrot from Mexico City.” The production actually used two parrots: one that was good at flying, and one that was adept at sitting on LL’s shoulder.

10. Deep Blue Sea reused some props from other films.

The plane that McAlester and Franklin fly out to Aquatica had been used in the Harrison Ford-Anne Heche film Six Days Seven Nights; Harlin had it repainted for Deep Blue Sea. The facility’s red escape sub had previously been used in another Samuel L. Jackson movie, Sphere.

11. The filmmakers used tricks to make the sets look like they were underwater.

Some of the sets were built on top of the Baja Studios tanks, and were designed to submerge. Others were built on sound stages, so the production designers put fish tanks full of water outside portholes and lit them to make it appear as though the facility was underwater.

12. Jackson’s big death scene became an instant classic.

Harlin really wanted to surprise the audience, and to do that, he took a cue from Alien. “Most of the cast is unknown, and the only person we really recognize is Tom Skerritt,” Harlin explained in DVD commentary. “He was the captain, and when things start going wrong, we relied on him ... he’s going to lead us to safety. And then halfway through the movie, he gets taken away, and it’s a shock and you don’t know what to trust.”

So Harlin cast Samuel L. Jackson early in the process with the intent of killing him off, and made the rest of the cast relative unknowns. “We cast Sam in this part where he’s very powerful, very smart, he’s the oldest of the group. You really think, he’s a movie star. He’s going to take care of business, he’s the one we can rely on, he’s going to be saved,” Harlin said. They made the character’s speech long and corny and pompous on purpose. “I knew the audience would be groaning and saying ‘Oh, come on, this is pompous,' but it had to be pompous for the surprise to work,” Harlin said. “It had to take you to a place where you get a little uncomfortable and start squirming in your seat, and saying, ‘Oh, these filmmakers are stupid, they think we’re going to buy this whole story.' It’s just a little too much. And just when we get to that place, we’re going to take everything away that you believe, and everything that you thought was going to happen in this film, and then you have the audience hooked.”

13. In the original ending, Saffron Burrows’s character lived ...

But test audiences, who saw the film less than a month before it was to open in theaters, hated it. “Basically what had happened was that the audience felt so deeply that the scientist character, the woman who was behind the whole experiment with the sharks, that it was all her fault,” Harlin said in 2013. “In their minds, she was the bad guy … I remember us all sitting down and going, ‘Holy sh**, we are in trouble. How do we fix this?’ It was my idea, I said, … ‘When she falls in the water, what if she doesn’t survive? She gets eaten by the sharks and L.L. Cool J is the hero. Everybody likes him, and Thomas Jane.’”

The team did a quick one-day reshoot in the Universal Studios tank. “We did some CG work on the sharks and stuff like that,” Harlin said, “but it was a super fast fix and it saved the movie because the audience got what they wanted.”

14. ... And LL Cool J’s character was supposed to die.

“He was originally going to be shark meat quite early on,” Harlin told the Reading Eagle, “but he was so good we kept him around.”

The rapper-turned-actor did many of his own stunts, and Harlin said he also complained the least out of all the actors. “LL was really determined to do a good job on the film, to do whatever it took to make it work,” the director said in DVD commentary. “LL was pretty great. He had some very uncomfortable situations because he really has to come face to face with the sharks a lot and even ends up in the shark’s mouth at the end of the film, but he was always game, he was really determined to show that he was not a rap artist who wanted to do little movies but he’s a real actor who wants to do something really powerful and interesting.”

15. LL Cool J channeled a shark in the music video for the movie's theme song.

He had a hard time putting in the contact lenses for the "Deepest Bluest (Shark's Fin)" music video.

16. There are a number of shark myths in the movie.

Harlin asserts in DVD commentary that “a lot of this information regarding sharks is very very accurate. Obviously because it’s a movie we take license with some of the stuff they’re doing [in terms of the Alzheimer’s research]… the fact is, sharks have been used a lot to study and find out why these creatures have been around for 400 million years, why they never get cancer, why they never sleep, why they never stop moving.” And maybe it was accurate, at the time. But now we know that sharks do get cancer, and although they don’t sleep like humans, they do have periods of rest. The idea that sharks never stop moving comes from the thought that they need to keep water flowing over their gills, or they’ll die, but that doesn’t apply to all sharks.

Deep Blue Sea’s makos somehow develop the ability to swim backward—and as one character notes, that is, in fact, a physical impossibility. No matter how big a shark's brain is, that's not going to change. You can enjoy a more thorough takedown of the film’s “science” and leaps in logic here.

17. Deep Blue Sea was the first movie Stephen King saw after he was nearly killed in an accident.

Mario Tama, Getty Images

“My first trip out after being smacked by a van and almost killed was to the movies (Deep Blue Sea, as a matter of fact; I went in my wheelchair and loved every minute of it),” he wrote in Entertainment Weekly.

This story has been updated for 2019.