Diver Dennis
Contributor
It's difficult to say for sure but I'll stick with anxiety. We really need some more information to give you more definitive answers. Just another reason to fill out your profile...*hint* *hint*...

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We had a woman with severe shortness of breath and chest discomfort on her first OW checkout dive, ....
I really wondered about anxiety. But she also complained of chest discomfort. Despite the fact that she never had asthma nor smoke - I do not think we should simply blame anxiety in when exertion and cold water is involved. I really think one need to look at cold and exercise induced asthma, ......
She wants to try it again next weekend. I surely hope that it is not asthma. I did warned her about it, but I am just a divemaster intern.
Hi,
When I first get into the sea and do my descent, I find that I have trouble breathing. I try and breathe normally - but I feel I'm getting insufficient air. I try and take deep breaths at this stage.
However after about 20 minutes or so- I start breathing ok without any difficulty.
When I get out my chest and possibly lungs hurt a bit.
On a dive to 20m, my air tank can last me up to 50minutes at least. My weight is about 78kg, height 5foot6. (170cm). Chest 100cm.
Am I doing something wrong?
Relax sipadiver,
First of all you want to be raking deep breaths and do so at a comfortable rate. As you relax and get accustomed to diving and then the dive the rate will slow and you will be content. This is probably where you are after 20 minutes.
When you first get into the water you may be pumped up from huffing your gear around. Breathing normal may mean sucking some air down. The one thing you do not want to be doing is breathing shallow. If you are pumped up when you get in the water spend some time on the surface face down chilling out with your snorkel or regulator. When you are mellow there it's time to begin the dive.
Not taking deep breaths is guaranteed to have you feeling short of breath due to carbon dioxide retention. Couple this with any anxiety or anxiousness to get on with the dive and you will not be a happy diver.
Your profile is little help (Hint to add some detail to it) but I will assume you are a new diver. If you are getting 50 minutes at 20m on a drop from a boat dive that is not all that shabby so stop beating yourself up.
You need to decide if the chest/lung discomfort worth seeing a doctor about. Speaking with DAN (you are a member right?) is also a good place to start.
How many dives does this pattern pertain to?
Pete