The sound of bagpipes fills the air, but as the clock ticks over to 7.12am, the music falls silent and is replaced by the blast of a horn.

Suddenly, 66 towels hit the ground as their wearers charge forward, nude, into Lake Burley Griffin, some with a gasp, a squeal or a yell.

"It's colder than the Derwent," one woman exclaims.

Swimming nude in the lake in the middle of winter sounds nuts, but these people took the plunge on Thursday morning for a good reason - the second Canberra Winter Solstice Nude Charity Swim.

"Last year, we had four [people], and we did it illegally," organiser Ian Lindeman said.

"We still raised $2100, but this year, we got through all the hoops and we're very, very happy with the turnout for two great causes."

Mr Lindeman said he expected this year's event would raise more than $10,000 for charities Lifeline and Love Your Sister.

Swimmers had to donate $30 to either charity to take part, but many had chosen to donate more, chipping in with $100 or $200.

While Mr Lindeman was now an experienced nude swimmer, having also taken the plunge at the Dark Mofo Nude Solstice Swim in Hobart two years ago, he said little could prepare you for the chill when you hit the water.

"Your feet get the coldest, that’s the worst part," he said.

"Bu it's a little bit spiritual. You get rid of your baggage from the last solar year and start refreshed.

"The days get longer from now on, so you come out re-invigorated. Everyone’s enthused and happy. It’s great."

Some participants raced in and out of the water in a matter of 30 seconds, but others lingered for well over two minutes.

A few even swam to a floating platform offshore and climbed onto it before jumping back into the lake.

"It was pretty cold. Colder than I thought it'd be," participant Glen Sinnott said, seconds after emerging from the water.

"My mate wanted to go all the way to the jetty, but I couldn't stay in there that long.

"I had to get back out."