What was scary and what could have made it scarier (More like this pls)

This movie was pretty creepy. I've RARELY been creeped out by a movie. It kind of reminded me of Sphere in a sense that there's so much mystery and intrigue to all that's happening. We need more movies like these. Anyway, on to it.

What made this movie scary:

1. the plot setup:

Set out on Europa, a harsher/further environment than Mars. There's no contact with the Earth, and there's nothing but a pitch black abyss below you and nobody really knows what's down there. YES, SCARY.

2. The pacing creates tension and intrigue:

There were some generic plot tricks in there made obvious, but the timing of sound effects, camera work, and importantly, what is not seen (At least until the end) gives that child like sense of "what is that I hear out in the darkness."

3. There's no CGI or overuse of special effects:

This helps ground you in realism. Once they start showing CGI squids tho that goes out the window. That brings us to the next part.

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How this movie could have been better / scarier:

1. (Obviously) They shouldn't have shown the entire creature in the end. What they should have done is show a dark figure in the water as it filled the cockpit and gave a glimpse of the bio-luminescence.

This would have left you with that child like "Wth was that?!" feeling & had the imagination going crazy.

2. They should have added greater traces to the creatures' intelligence. This would have shown the creatures were even more capable in addition to being hostile.

3. They should have added some Sphere / Interstellar type plot twist to add some ending intrigue, and re-watch value. Showing a generic CGI squid at the end was probably the worst way to end the movie.

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I really wanna see more sci-fi movies like these. It was awesome.