Interesting concept! 

I like what was done with the music and how depth affects it. I also like how everything gets darker deeper down. I think the shark was a nice touch! 

I feel as if the UI should be a little more clear on what exactly is going on with decompression as I personally had trouble understanding that mechanic. It was slightly confusing and I would imagine would be confusing for anyone who plays that doesn't have experience/knowledge of how diving works.