Starting in July so that September is not a shock
I have swum in the sea on holiday most summers of my life and called it cold, and I have never swum in anything below about 17 °C on purpose. The plan this year is to start now, in July, when the lake is as warm as it gets, and then not to stop. If the water drops a degree every week or two, the theory goes, there is never a day when it is suddenly too cold, only a day slightly colder than the last one. We will see.
The lake read 18 °C at the jetty this morning at half past seven, which seemed warm enough to need no thought at all. I was wrong about that in an instructive way. Walking in slowly, the cold reached my stomach and I gasped, properly, an involuntary intake of breath I had no say in, followed by ten or fifteen seconds of fast, shallow breathing that I had to consciously slow down. That is the cold shock response, and it happens, I now know, at any temperature that is a sharp step down from the skin, which includes a summer lake on a cool morning. It passed. I swam for twenty minutes, out to the first buoy and along the reeds and back, perhaps 500 metres, and got out feeling better than I have felt in months.
Things I did right by luck or by reading: I walked in rather than jumping, so the gasp happened with my feet on the bottom. I had a bright tow float, bought the week before, clipped to a belt, so that the two anglers on the far bank could see where I was. I swam parallel to the shore rather than across the lake. I had a towel and a warm top within reach of the water and a flask of tea in the bag.
Things I did wrong: I went alone. There was nobody on the jetty and nobody who knew where I was, and I was twenty minutes in open water for the first time. A friend has agreed to come on Sunday and I have found, by asking at the café by the car park, that a few people swim here every Sunday at eight. I will be there.
I have bought a thermometer on a string and a notebook. The first line in it reads: 6 July, lake, 18.0 °C, 20 minutes, alone, gasped. The plan is to fill it every week until the number at the front is a single digit, and then to keep filling it.