WINDERMERE'S temperature warmed to a welcome 17.5 degrees as thousands of swimmers took the plunge in Britain's largest open-water event.

The three-day Great North Swim - which began on Friday - featured a variety of distances for swimmers of all ages and abilities, with the elite men's and women's races taking place today.

But the first day was edged with sadness after a 52-year-old man from Wallington in south London collapsed and died in hospital after completing his swim.

Held in partnership with British Swimming, the race is seeing the country’s best senior and junior athletes competing to qualify for a place at the European Championships or the World Youth Championships.

Top British athletes included 2013 Great Swim champion Tom Allen, 2013 European Junior 5km champion Alice Dearing and 2012 European Championship finalist Lucy Campbel.

They were joined by some of the best open water swimmers from around the globe, including: 2013 World Championship gold medallist Christian Reichert of Germany, 2013 Australian National 5K Champion Michael Sheil and 2011 World Championship gold medallist and two time Olympian, Swann Oberson of Switzerland.

Alongside the elite swimmers amateurs of all abilities took on their own personal challenges over half-a-mile, one mile, two mile or five kilometre distances.

They included the official 2014 Great Swim ambassador, Coronation Street star Catherine Tyldesley, who admitted being 'terrified' before taking the plunge on Saturday.

After completing her swim, she told the Gazette: "I really, really enjoyed it. Before going in I thought I was really going to hate it but it was just a really great atmosphere and everyone's cheering you on.  And the water was nowhere near as cold as I thought it would be.

"It feels quite exhilerating when you get out, especially being scared of it - because I was terrified. So I'm quite proud of myself."

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Also making a non-swimming appearance on Saturday was Olympic gold medalist Rebecca Adlington, who signed autographs and posed for photographs with fans before the start of today's first swim.

She was accompanied by a TV crew making a 60-minute Great North Swim documentary for Channel 4, which is expected to be shown on September 6.

One of the first day swimmers was Colin Hill, who is director of Wray-based Chill Swim, a company which organises and promotes open water swimming events around the UK.

"The conditions just couldn't be better," he said. "The water was nice and calm and over 17 degrees, which is pretty good. "

Since 2008 the swim has grown from 3,000 participants to around 10,000, which the organisers say clearly demonstrates the increasing popularity of this exhilarating sport.