[netaustin]

Yes. The first time it happened was in the Hudson River in the NYC triathlon. I thought for sure that I'd just ingested some sludge, and I went on to complete the race, after which I was sent to the hospital (I walked). My pulse ox was 86. Most triathlon deaths occur during the swim portion of the race and are attributed to cardiac events, often SCD, but pulmonary edema may actually be the primary cause. A teeny bit of education (chest congestion? get out of the damn water!) could save lives, but nobody in the business of triathlon wants to scare off new participants, since the amateur fee-paying end of the sport is really the whole game.

[TrevorJ]

Wow, I had no idea. That would not have been on my list of potential dangers from long swims at all!