In between lockdowns, on a miserable, cold January day, I took myself off to Clevedon, a coastal town near me on the Bristol Channel. I wrapped myself in warm clothing and walked to Marine Lake, a seawater pool built onto the natural coastline. To my surprise, I saw a group of giggling women emerging from the ice-cold water. Spluttering and chatting away, they awkwardly changed into their clothes under their towels. I stood and looked on in disbelief: it was freezing, but they were jubilant, defying the weather by going for a swim.