Sci-fi horror movies like Underwater and Sea Fever prove that the genre works better without a space setting. The reason for this is that outer space settings are harder to relate to. The closer a sci-fi horror movie is to life on Earth, the easier it is to accept. This makes them more frightening. That's not to say that sci-fi horror movies with an outer space setting are not frightening. The movies of the Alien franchise are mostly set in space and planets other than Earth; they are arguably some of the most frightening movies out there, especially Ridley Scott's 1979 original. However, considering that most people have never been to outer space, sci-fi horror movies set in space are harder to accept. Granted, any movie that features extraterrestrial life is harder to accept for mainstream audiences, but the outer space setting doesn't make it easier.

For example, if the original Alien movie had been set on Earth instead of on the Nostromo in outer space, it would mean that the Xenomorph could be living in the house next door, or worse, in the bedroom closet, both of which are more frightening places for the Xenomorph to be found compared to planet LV-426. In other words, aliens and other supernatural creatures are a hard sell for most people, and aliens in outer space are that much harder. Audiences are more easily frightened by what they can imagine happening in real life, with alien invasions being just slightly more believable than an alien attacking a spaceship. Essentially, with fewer outlandish story elements to accept, the easier it is for the audience to become immersed and thus frightened. Following this theory, the best horror movie villains would be those that most closely reflect the audience's own image.

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Sci-fi horror movies with an ocean setting provide a good example of why those set in space aren't as scary, in comparison. Underwater and Sea Fever both have an ocean setting (the former underwater, the latter above). If these same movies were set in space, it's easy to see why they would be less frightening. In a space setting, Underwater would swap out fears of drowning and enclosed spaces for the airless vacuum and vast void of space. The fear of drowning and being trapped underwater are much easier for audiences to imagine, and mainstream audiences can't fathom the horror of being lost in the vacuum of outer space. It's safe to assume that most audiences would imagine it to be a lot like drowning. In this way, outer space is a surrogate for the vast unknowns of the Earth's oceans.

Hermione Corfield and Ardalan Esmaili in Sea Fever

Likewise, if Sea Fever were set in space, this would drastically diminish one of the movie's most central threats: contaminating their world with the titular sea fever. In space, the threat of contagion is always harder to imagine since there are so few humans in space in real life. Despite the facts that the Earth's smallest ocean is approximately 6,200 miles wide and the distance to outer space is only about 62 miles, most people perceive the ocean to be closer than outer space. This perception of the ocean is why Sea Fever works so well; the ship's crew and the threat they face are grounded in the realities of working on a fishing boat. Likewise, Underwater introduced an ancient, Lovecraftian monster that lives below the depths — Cthulhu. Cthulhu's existence echos the audience's fears of the unknown and what might be lurking leagues beyond the water's surface.

For any given sci-fi horror movie, the likelihood of it being frightening is directly proportional to how close to reality it is, which is why filmmakers strive to incorporate familiar elements into movies. In Alien, for example, the crew members of the Nostromo were styled to look more like a group of truckers than astronauts, grounding the movie in reality. Placing the crew on Earth would simply be taking this concept one step further. It's important to emphasize that an Earth setting doesn't guarantee a more frightening movie — there are many variables that go into what makes a sci-fi horror movie scary. Essentially, sci-fi horror movies like Underwater and Sea Fever show that the legitimate fears associated with space can be explored more easily on Earth.

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