Seeing as we've been talking open water....
First open water swim of the year :-)
I was signed up for the latest of a local aquathon series. 400m pool swim and a 4ish mile run. However an open water group I know was in the area and swimming a small lake near me. I spent a while deciding which to do. I spent a while trying to get the wife to suggest I do both....
'nuff said... I had to chose. I dropped the aquathon. Justification being I had a wetsuit and some other kit I hadn't tried out yet and I've still got another (the last) of the aquathons , next month
I'd read about cold water acclimatisation and I had some experience of being in cold water from a few years ago, when I kayaked. I got to the bank with mental images of the experience being 15 minutes shivering along with 'ice cream headaches' .
As it turned out, it was a very different experience.
The lakes an old floodplain, generally 5-6' deep, the bottoms quite muddy so the waters not exactly clear. Initially there wasn't that much actual swimming. A bit of floating (it's great how much extra buoyancy a wetsuit gives!) and then a few of us agreed on something to 'sight' and headed off, which was repeated. Probably only a few 100m in all and about 30 mins in the water after taking the initial plunge. I wasn't uncomfortable, hands felt OK, without gloves.
At this point, I decided to call it a day. Better to get out feeling OK than 10 mins later shivering?