It used to feel like a big ocean.

Below.
7/10. There should be more submarine-based horror movies. Tense and claustrophic by nature of its surroundings, a 'who knows what?'-mystery and a 'what the fuck is happening to us'-horror. Sometimes it gets cheap, both with CGI and certain thrills, and there are some connective scenes missing that seem to accidentally create new, unnecessary mysteries, but there is a very solid, very interesting movie inside the capsule.