You have a really strong base here for a great horror game, but there are a few problems. First, the controls are too complex and introduced too quickly - a more in-depth tutorial or at least a quick reference guide would be super useful. Second, the side radar faces forward and the nose radar faces sideways, which is confusing. Third, there doesn't seem to be much to do? Maybe the sub was just too slow and my patience too thin, but I wandered around the game for a good half hour looking for something interesting. I found some stuff on the x-ray but nothing ever game of it - just some green lines on a new scanner. I certainly didn't feel like I'd accomplished anything - and with no monsters, there's no threat, and thus no scares. Ultimately, the game just feels unfinished - like this is an alpha build or a proof-of-concept.
All that being said, I'd love to see more of this, with the monsters in full swing and a working tutorial. The mechanics, though inscrutable at times, are absolutely fascinating and the sound design and voice acting is absolutely impeccable. The bones of this game are really strong, I just wish there was more meat on them.
(Also, there's no quit button. The REAL horror was being trapped in the game all along!)