Hi,
I'm an open water swimmer, with the dubious speciality of winter swimming (a la Lewis Pugh) although the coldest water I've swum in bare-skin was a sub-tropical 4.8C (just over 40F).
I had the privilege of featuring on BBC1's Countryfile programme where I swam in just my Speedos in the River Mersey on St Valentine's Day, 12th Feb last.
This winter I may get the chance to first break the ice.
I was one of the founder members of RALSA (River and Lake Swimming association) and maintain the water temperature records.
Wildswimmer Pete