The movie is set in the year 2027

In designing the creature of the film, Stan Winston and George P. Cosmatos went through a mini-library of marine life pictures and medical reference books. They were inspired by the physiology of the natural world, and came up with the idea of combining human body parts and elements of deep sea marine life into an unnatural creature never seen on film before.

There are very few scenes in the film that were actually shot underwater, as production went for the "dry for wet" look, with most of the scenes inside the Shack taking place on soundstages and a tank measuring 130ft x 270ft.

According to the sleeve notes on the DVD, a dry for wet lighting test by Alex Thomson used an old army tank for the wreck of the Leviathan,and some make shift diving suits were made using padded football suits and helmets from 2010 (1984).The final suits in the film were designed by Steve Burg and built by Stan Winston's crew.

Deep Star Six (1989) was the first release of several underwater-monster-themed feature films released during 1989-90, including The Abyss (1989), Leviathan (1989), The Evil Below (1989), and Lords of the Deep (1989), and 'The Rift' (aka 'Endless Descent', 1990). With the exception of 'The Abyss', none of these films were box office hits.

Not only does this film have a similar theme (deep ocean scientific studies) to DeepStar Six (1989) which was released the same year, but the plots are also almost identical: The science team comes across an unknown organism in extreme depth, it hunts them one by one, and finally follows the few survivors up to the surface.

While much has been written about Doc's (Richard Crenna) Latin quote, a fast and loose translation of, "Natura non confundenda est" is "Nature is not to be confused".

Chicken feathers were used at one point of shooting the underwater sequences to suggest things were floating around in the water. According to Alex Thomson this did not work because the feathers floating side to side instead of up and down and the idea had to be scrapped altogether.

Hector Elizondo's character of Cobb is named after the film's production designer, Ron Cobb. Also, Michael Carmine's character of Tony 'DeJesus' Rodero, shares the same last name of the film's first assistant director, 'Kuki Lopez Rodero'.

The book Steven Beck reads is "The One Minute Manager" by Ken Blanchard and was a very short fad-management book which was popular in the 1980s.

One of six underwater-themed sci-fiction monster movies released around 1989/90. Others include: The Abyss (1989), Leviathan (1989), DeepStar Six (1989), The Evil Below (1989), The Rift (1990), and Lords of the Deep (1989).

Second time that Richard Crenna worked with George p Cosmatos after Rambo first blood part 2 which also had Jerry Goldsmith music.

To create the look of the creature, the Stan Winston Studio design team drew inspiration from marine wildlife and medical books. Given the monster's ability to "assimilate" its victims, the SWS artists zeroed in on a concept that combined human body parts with the anatomy of various types of deep-sea marine life.

The creature effects team encountered some language differences during the making of Aliens (1986) in England, but the challenges were much bigger in Italy. "I always keep a log of everything we order on shows, just in case accounting comes back later and asks about it," noted lead creature effects mechanic and on-set technician Richard Landon. "In my log from that show, you can tell that there were some real language issues, because a lot of times, instead of words, I drew pictures of nuts or bolts or that kind of thing. I would quite often have to draw a picture just to make it clear what I was talking about." There were cultural differences too, such as the Italian's crew tendency to drink large amounts of red wine at lunch. "They'd say, 'Here, have some wine!' remembered Mahan, "and we'd say, 'Uh, thanks, but we're not allowed to drink while we're working.' Of course, every once in a while, we'd sneak a little, but nothing like the way those guys were drinking it down."

Scenes that could not be filmed dry-for wet at the soundstages of Cinecitta were shot either in big water tanks or at sea in Malta. Stan Winston had his main creature effects team trained and certified as scuba divers prior to filming in order to support the required water scenes in the movie and to ensure their safety and proficiency in the water. "Tom Woodruff, Jr. would be in the suit underwater and the rest of us would act as safety divers so we could get Tom out of the suit quickly if something happened," noted John Rosengrant.

Once, during the underwater photography, John Rosengrant and other members of the SWS on-set crew were underwater for so long and at such depth, that they were unaware of a violent storm that had come in, threatening to rip the topside boat from its anchor and smash it against nearby rocks. "We had no idea all of this was going on, until we came to the surface and saw all this commotion," recalled Rosengrant. "We all go out of the water and helped to push the boat away from the rocks and hold it steady in this storm."

Hector Elizondo and And Lisa Eilbacher have appeared in Beverly Hills Cop Series

"The Leviathan design," said Stan Winston, "essentially blends fish-like creatures with humanoid elements. We did a lot of anatomical research. Every creature effect starts from a realistic element, otherwise it doesn't look right. But we're using marine life and human anatomy in a way that you wouldn't expect."

After Winston and director George P. Cosmatos selected the final creature design, the SWS team began to conceive the creature in three dimensions, first as a small-scale design maquette, and then as a full-scale sculpt. "It was really kind of a beautiful sculpture, because of all the different weird creatures combined in it," said Leviathan FX team member, Shane Mahan. The unique creature would be brought to life on screen by SWS crew member and suit performer Tom Woodruff, Jr. inside the creature suit, along with additional puppeteered elements.

"Leviathan was kind of The Thing underwater," said Mahan, who worked as lead creature effects artist and SWS on-set technician. "The deep-sea mining crew members begin to mutate and kill one another, and each body is absorbed into a conglomeration creature that has three or four different bodies combined with all of these sea creature elements."

After building the creature and the dive suits, a small Stan Winston Studio team followed the production to Italy for four months of filming at Cinecitta Studios in Rome. The famous studio, where director Federico Fellini made films like La Dolce Vita (1960) and Casanova (1976), was especially meaningful for Mahan, a longtime Fellini fan. "The whole time we were at Cinecitta," remembered Mahan, "I'd be out in their junkyard in the back, looking for old Fellini props. All of these massive props from Fellini films were just laying around, giant elephants carved out of foam, which I think were from Intervista (1987). We had a blast going through those old props at Cinecitta."

In addition to the amazing creature effects, Stan Winston Studio also built the deep dive suits, designed by conceptual artist Stephen Burg. The studio made a dive suit for each of the lead actors, Peter Weller, Amanda Pays, Ernie Hudson and Daniel Stern. "We were commissioned to build the old-style mechanical underwater dive suits that the crew wears to explore the sunken ship," said Mahan. "We made one custom suit that could be retro-fit to every actor. The suits were white fiberglass shells with joints. They weren't as light as the actors probably would have liked, but they were as light as we could make them, considering how big and bulky they were. They had bellows at the bottom of the feet, so when a character stepped down, they would squirt air to make the dust on the ground poof out. Shot at forty-eight frames per second, it looked like it was slow-motion and underwater."

The experience was an adventure and a joy for Stan Winston and his monster-making team. Not only did they get to live in Rome for four months during filming, and even learn scuba diving, a recreational activity many of them continue to pursue to this day, but they also got to work with a director who was unusually generous with inviting their input. In addition to producing the creature effects, Cosmatos trusted Winston to direct the second unit action sequences. "George Cosmatos always let us take the lead in how to shoot the creature," noted Landon. "He was such a big-hearted person, he would throw up his hands, and say 'I don't know what I'm doing.' He'd just admit it and let us do what we knew how to do. We know what our characters can do and we know the best way to use them. We're thinking about what our characters are going to have to do on the set the entire time we're building them. So we are goldmines of information and knowledge. Some directors recognize that, and really rely on us."

When Doc is analyzing Sixpack's skin sample, the computer reports back the phrase "of unknown origin". This is a winking nod to director George P. Cosmatos and star Peter Weller having previously collaborated on the movie Of Unknown Origin (1983).

50 to 60 spec drawings of the potential look for the creature were submitted to director George P. Cosmatos. All the drawings were combined for the final definitive look for Leviathan which was a huge, fish-headed beast with dagger like teeth with the ability to absorb recognizable characteristics from its victims.

Near the beginning of the movie, when Tony 'DeJesus' Rodero's oxygen is about to run out, the captain tries to do something with a computer on board. Between 3D animations and strange interferences on monitor, we see Luxo, Pixar's logo, with a ball, like in the first ever short film made by Pixar Luxo Jr. (1986).