Cold water, high altitude
This week I went for a swim in a cold lake (65F/16C) at 7,000 feet above sea level. The air temperature was about the same as the water temperature. I live at about 2,500 feet, and I'd been in town for less than 24 hours before my swim.
I'm used to really hot air temperature (100-110F, 38-43C). Water temperatures below 90F/32C feel delightfully refreshing to me.
I expected to swim slowly at that altitude and have less endurance than normal. I also expected the water to feel cold when I jumped in but that I would acclimate pretty quickly. 65F/16C doesn't sound comfortable to me, but it doesn't sound that bad.
Things went pretty much according to my expectations, except I never felt happy during that swim. I didn't feel out of breath or cold, but my form was off, and I was just trying to get thru and be done. I swam a really tight loop around the boat dock--no interest whatsoever in swimming further out.
I wanted to stay in for at least 45 minutes, but after 30 minutes people started launching boats. Since I didn't feel good about leaving that spot, I decided to get out.
When I got out, I felt dazed and *extremely* breathless. I didn't feel cold until about 20 minutes later, and then I stayed cold until I took a long, hot shower about 2 hours later. Both of these things came as a complete surprise.
I'd be interested to hear others' experience/insight on this.