Although things may be different from place to place, i was taught to remove the mask from my head when in distress. I see divers all over with them on there forhead and i only way something when they look "odd" but usually there just floating around, laughing, talking, or prepping to submerge. This is something i cover (usually) with new dive buddies and leave it at that. Its not worth yelling at someone if they are visibally ok and their mask is on the forhead. I do place mine on the back of my head out of training and habits. Also i agree with Smitty on this one, you would have no trouble identifing me if something is wrong...