Not quite a Speedo, but

[Torchwatch]

Remember reading tales of rock climbers in the 1960's, one had a memorable woolly hat that was used for many purposes including as a bag for raising chock stones and as swimming trunks. Quite how you use a woolly hat as swimming trunks was never explained, but it all happened in the tarn at the base of Clogwyn Dur Ado (the black crag) on Snowdon.

I have actually swum in one of the tarns on the steep side of Loch Ness, a very lonely place where only deer and sheep visit, the water cold and peat black, and the weather turning towards rain. I even had a woolly hat with me that day.