Ah yes... I seem to recall that directive in most open water manuals for most agencies
You have to keep an open airway. Your glottis has to be open to your lungs. If you are not actively breathing, then it would be closed. If it is closed...then you are at risk of a fatal injury.
Why screw around with this?
Breath continiously and
never hold your breath.
It sounds pretty damn simply to me......
lionsandtigers.... if you are going to make sweeping statements on a global forum, that could effect people's lives and safety.... perhaps you would care to substantiate them with a few medical references, agency directives, DAN reports....etc etc etc
Otherwise, please remember that inexperienced divers read these forums....
Actually, she's right ... it's simple physics.
But you are also right ... the rule "never hold your breath" exists for a reason.
So let's talk about that reason.
New divers are taught a lot of "rules of thumb" that directly impact their safety. The "never hold your breath" rule is based on the fact that air expands as you ascend, and that your lungs ... with your glottis closed ... are a closed system. Remember the expanding balloon that most instructors use as an example in basic OW class. The rule exists because the alvaeoli in our lungs are extremely fragile, and there's no pain centers down there to tell us when air expansion is on the verge of damaging them. So it's extremely important for newer divers ... who usually struggle with buoyancy control ... to adhere to this rule for their own safety.
Fast forward to when those same divers become more experienced, have their buoyancy control down pretty well, and have taken up photography. Do the same rules apply? Should they?
The answer is ... as with most things involving scuba ... "it depends". Even if you can manage your buoyancy quite well, excessive breath-holding can lead to a buildup of carbon-dioxide in the bloodstream ... and that can create a few different issues for the diver at any level. So you want to be careful not to overdo it. But let's face it ... as our buoyancy control improves, we DO use our lungs to fine-tune that control throughout the dive by modulating (and moderating) the level at which we breathe to increase or decrease our state of buoyancy. Experienced divers learn how to pause briefly between inhale and exhale to enhance the O2/CO2 exchange on each breathing cycle. Experienced underwater photographers do, in fact, learn how to modulate ... even pause ... their breathing to hold in a particular position while taking a shot (and as someone pointed out, to avoid the effect of bubbles during the shot).
The trick isn't to "just say no" ... it's to moderate your behavior and to understand what the potential risks are. Specifically ...
- "Never hold your breath" really means "never close your throat" ... and it's simple to stop breathing without closing your glottis. The important thing is to know that's what you need to do.
- Never ascend while holding your breath ... because even those who are experienced at doing it may, in a moment of complacency, close their throat ... and it doesn't take a whole lot of air expansion in your lungs to do damage. You won't feel the damage happening ... there's no nerves down there to give you that kind of feedback ... until it's too late.
So ... to answer the OP's question ... yes, most photographers DO stop breathing while they're taking a picture. If you don't, then you have to contend with minute changes in buoyancy at a time when it's important to be holding critically still in order to frame the shot you want. However, before you attempt something like that you should make sure you have solid buoyancy control skills and that you have developed your awareness to the point where you can pay attention not just to your shot, but to what's going on around you.
In other words, it's an advanced skill ... one that new divers shouldn't, for their own safety, be doing.
Like most things ... the rules change as you gain experience and expertise. Take it a step at a time ... it's just safer that way.
... Bob (Grateful Diver)