make quicksand have overlay texture under surface

if you go under quicksand in BOP it looks like your underwater and can see everything, this needs to be fixed so you can't see anything under quicksand...

Ideally I'd like to do this for all of our liquids, I'm just not really sure if it's possible.

@Forstride - have a look at the lava source code, something in lava controls how foggy it is under lava and that should be changed to make quicksand so foggy underneath you can't see anything...

under lava surface

under QS surface

Closing this because we either can't/won't fix it or it's not an issue in 1.13