Let me start off by saying that I probably didn't buy this for the same reason that most other people did. I wanted to find a way to be able to play my music in the shower and I thought that my phone and this case might be the way to go. I almost expected to be let down, but it actually works! I now just slip my phone in this case, which is connected to the shower head, and then close the case and play my music.
For me, the best thing about this case is that the sound comes through it as though it wasn't actually there. I don't know what type of plastic is used on this case, but the fact that this seals in my phone and is still able to project the music from my phone's speakers is pretty darn cool to me.
As far as being able to be submerged in water, I'm not sure how well it does in the ocean or in a pool, but I have sprayed plenty of water on it in the shower and not once has my phone been touched. Going by all of the other reviews that I have read about it, I think it will pass just about every waterproof test that people can throw at it.