A small outline of the equipped diving goggles should be visible in 1st person when diving. This should go a long way to make diving feel more claustrophobic and immersive. Maybe even the glass of the goggles should be visible (barley of course).
Like with night vision I think it is important the player "feels" that he is wearing his diving goggles to make him more conected to his gear and the simulation in general
Yes it would be great, if only to make a larger difference between being on land and underwater apart from fog 20m away
Agreed, this effect is already implemented when putting on NVG's, when you get tunnel vision.
It's also important for ballancing. Because the limmited vision affects the combat between Divers!
The military style goggles are usually black rubber on the peripherals. Civilian goggles are typically a translucent rubber, but not usually clear, and really aren't see through. Some versions of goggles do have peripheral lenses that widen your field of view. Since they only have one type modeled in game though, I would start with that, and they have black rubber that blocks the peripheral view.