Check the sea-grass in that same picture, as already mentioned, there appears to be quite a current running, which would push the bubbles from exhalation back behind the diver's head. I'm guesing this has happened here - you would hear and notice that much bubbling from a first stage.Dig:I agree with Theredhead, the diver with the attachment on the top of their snorkel looks like they're first stage is a bubble machine....something I'll keep in mind to check my buddies for, I learn something everytime I get on this forum.