This was such a fantastic experience. First off, the lighting is absolutely dialed in. Also really liked the subtle water shader, just a nice touch. The movement mechanics were all really unique I think, and definitely could provide for some interesting tense, puzzle-like gameplay if expanded on. Overall, this was a super polished experience. As soon as I opened the game and was presented with the title screen, I could just tell it was going to be a quality game, and it didn't disappoint!
Also, couldn't tell if it was just in my head, but does the reverb/echo on the sound change when you go into bigger or smaller spaces?