Across the UK at this time of year groups of people are taking to the seas, lidos and rivers. So what is it that makes them give up a warm fire and It's A Wonderful Life for a dose of cold water?
"You're going to hyperventilate," Lewis Gordon Pugh warns the 40 swimmers in Santa hats, hovering on the edge of a north London lido.
For those gathered to sample the delights of a December dip the loss of circulation is inevitable, but there had been a hope they could keep their breath. It appears not.
The water they are about to enter is seven degrees, which makes it 20 degrees lower than your average sports centre pool.
So it's fortunate that Pugh, a man who is no stranger to cold water, is on hand to offer a motivational speech.
This year Pugh completed swims in all five oceans of the world at the North Pole, where he swam a kilometre in water as low as -1.7 degrees.
"I've never, ever, felt such a violent physical assault on my body," he tells the gathered swimmers.
And there are a few worried faces when he reveals that the reason his hands swelled up was because the water within froze and expanded.
Pugh has the advantage of what he describes as a "Pavlovian response", his core body temperature rises by two degrees before he enters cold water.
No such luck for the mixture of veterans and newbies at this lido. So why are they here? Neil Jeffreys, a lorry driver by trade, came because he loves swimming outdoors. He finds indoor pools humid and he "likes a challenge".
Talking to the swimmers it becomes clear that it's the outdoor aspect that attracts them, rather than a love of cold water. It's even true of Pugh himself.
Lewis Gordon Pugh offers advice to a swimmer
"People say I thrive on the cold. Nothing could be further from the truth. Anyone who says they love the cold has never been cold before," he says.
The organiser of this event, Kate Rew, describes the feeling when she jumps in "like needles being pressed in all over my body". That may not sound like a lot of fun but it seems that after the initial shock things start to improve.
"Suddenly you get a feeling of your circulation kicking into gear. You're awake, you're alive, it's a great feeling," she says.
Those planning some cold water swimming this Christmas are advised by Ms Rew to prepare in advance. She says that water under 12 degrees requires a gradual acclimatisation process and you should only stay in for 90 seconds.
The swimmers have been told by Pugh not to "dilly-dally" and putting a foot in to test the temperature is a big no-no. So, with a loud "1-2-3" the swimmers plunge into the water.
There's splashing, a little spluttering but a notable lack of screaming as they enter the water.
Most of the 40 makeshift Santas are quickly back out. But the presence of Pugh spurs on some to stay in longer. They would look like anyone enjoying a swim at their local pool if their hands weren't quite that shade of pink.
Swimming Santas embrace the cold
"That was amazing" says one swimmer, another announces he wants to do it again and a suspiciously blasÚ swimmers say "it wasn't as cold as I thought it would be".
Naomi Branston describes the dip as "bracing" but has been in much colder water.
She's part of the team behind the World Winter Swimming Championship 2008, an event which is to be held in the UK for the first time.
Earlier Pugh had told the swimmers he had sped from his North Pole swim to a hot shower and everyone is keen to follow the expert's example.
And, in scenes that will be mirrored at outdoor swimming events across the UK, the rejuvenated swimmers round things off with a warm drink and mince pie.
Below is a selection of your comments.
Its not like the old days is it? I did my first "Looney Dook" when I was a teenager, but now aged 25 I say its gone too pop.
In '97 aged 14 it was a good laugh; a small pub full of people having a wonder down to the beach with a sewage outlet just 50 yards down the coast. At the millenium there were BBC TV crews and fancy dress and I even got on the Scottish evening news (I wore the saltire hat). That was my last time. Now it's too big. Last year 500 people went in the water and its great so many can have a laugh and raise thousands for a Childrens charity, I just miss the original have-a-go spirit.
It is still the best way to blow away the hangover blues!
Duncan, North Queensferry
I think it's a great way to welcome in the new year and aren't all the footballers swearing by this treatment for sore muscles and getting the blood circulating quicker.Brill
Beth Ackroyd, Essex
Myself and another 399 or so took part in the annual Mike Moyles memorial swim in Bude on Christmas day. As a newcomer it's certainly a shock to the system when the first wave breaks above the knees but as a start to the day I found it incredible and will be repeating the madness next year!
David Holder, Bude, North Cornwall, England
I was amazed when I first moved to Finland to see the determined winter "dippers". These hardy Finns go out every day in sometimes -20C or colder, lower themselves solemnly down municipal-provided steps at the end of little piers, into the water. Often their swim length being limited by the size of the hole in the ice! In bad winters the swimmers have first to shoo away the gathered ducks (and one time I heard of a muskrat). All this is carried out in a matter-of-fact fashion. After a couple of minutes, the good folk walk (not run) to change in small bathing huts, then go off to work, feeling - I am told - refreshed and invigorated. I'm assured that it bestows longevity. Since the Finns also believe this of their sauna indulgence, which can be upwards of 100C - maybe their is a link to long life and frequent exposure to extremes of temperature. I haven't been tempted to experiment yet.
Heather Fowler, ┼bo / Turku, Finland
I'm staying in heated pools and on warm beaches!
Ian Sedwell, Weymouth, UK
One word. Mad.
Amanda collett, buckingham.