I'm always glad to see a horror game take place underwater, since I think it's a drastically underutilized horror setting. It's actively hostile to human life, it slows down movement and dampens the soundscape, it allows for either claustrophobic 3D mazes or bottomless voids where anything could be lurking, and it's home to so many horrific creatures. I think that anyone growing up playing Ecco the Dolphin or Sonic the Hedgehog as I did will have a deep-seated fear of the open ocean and drowning in video games.
I thought that this game was very well done. In particular I like the touch of adding particles floating in the water, which not only helps to sell the underwater setting, but also gives the player plenty of things to see out of the corner of their eye.