Jes - I want you to know that I just walked away from my computer to take compose myself before responding to this because my first reaction was...
WTF was she doing goin for an OWS alone?
Now that I got that off my chest.
I would guess that it started out as shortness of breath from the suit. That's not uncommon and you will get used to it with practice. Likely during the SOB episode you inhaled water. Asthma will usually start out as wheezy and doesn't get rattly until later.
To get used to OWS with a wetsuit I usually have people go out and breast stroke until they are sure their breathing is even, then we do face in the water for 10 to 20 strokes and check in again by breast stroking. If all's well, then you can go for it.
It used to take me 3 trips to the lake in the spring before I could get in the water and just start swimming without hyperventilating.
Living life like there's no tomorrow.
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2007 Look Dura Ace
2010 Custom Tonic cross with discs, SRAM
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2014 Soma B-Side SS