Talking about extreme cold water swimming, the Endurance Challenge is the toughest event at the UK Cold Water Swimming Championships hosted by the South London Swimming Club.
The 4th UK Cold Water Swimming Championships will be held on January 24, 2009 at Tooting Bec Lido, the largest open-air swimming pool in London (90 meters x 30 meters) first opened in 1906.
The Endurance Challenge is 5 laps of Tooting Bec Lido or a daunting 450 meters in nearly freezing water. To qualify, a swimmer must confirm their cold water swimming experience that includes a 1K swim or 13 minutes in water 6°C (43°F) or less.
For more information on human adaptation in extremely cold water, Vladimir Lioutov of the Moscow Regional Centre has put together some fascinating information here (in English) on the "Human Adaptation In Extremal Conditions of Water Immersion".
Photo from the Moscow Regional Centre website.