Thank you for sharing this. Both frightening and helpful. One reaction: why is triathlon swimming worse than other swimming? Lots of people swim in cold open water. I suppose triathlon may represent the greatest concentration of such people in any one place (there aren't many 2000-person-strong open water swims going on world-wide). Another reaction: I don't buy the "IM is to blame because we sat around for 2 hours wearing wetsuits." The logistics for IM NYC were famously (but, to be fair, predictably) horrible. But I'd never put my suit on 2 hours before a race! At a minimum I would keep the top unzipped until, say, 15' before the start. Third: the number of people I know, strong athletes all, who have had chest-tightening experiences in a triathlon swim is very high. My closest was hyperventilating in the first 100 meters of the Timberman swim in New Hampshire before deliberately slowing everything down. No idea if this is a controllable phenomenon, although the author's experience suggests it is not.
it has definitely happened to me. I have never been able to untangle how much of it is physiological and how much of it is mental. When you get tense in open water all sorts of bad things happen . . .