Meanwhile, there are plans for a floating lido on the Thames. 'Indoor swimming pools are like Big Macs. Wherever you go, the water temperature and experience are the same,' Murie says. 'Lidos, on the other hand, can vary in temperature with the seasons, from 29ºC in the summer to 3ºC in the winter, which makes swimming more of an adventure.' Cold-water enthusiasts and sunbathers, take heart.