You may call them courageous, foolhardy, admirable or just a little odd, but thousands of fundraisers are preparing to take the plunge into the winter sea.
Jim Young emerges from the sea at Rotherslade Bay on Gower
These fixtures of the festive calendar see the committed rush into the water, often in all manner of fancy dress, splash about for a minute or two and retreat to the shore for a well-deserved warm-up.
But what motivates those even tougher souls who enjoy a chilly dip most days of the week, all year round, even when there's no deserving charity to benefit?
Jim Young, 59, is so passionate about his regular swim he and his wife have bought a beach hut at Rotherslade Bay on Gower, on the south Wales coast.
He has been braving the cold waters for the last five years. Now, changing is easier and he can have a warming mug of coffee brewing for his return.
"You've got to steel yourself to do it, but when I am in I always think it's not so bad," he said.
"It's usually at its coldest at the end of February or the beginning of March.
"Every day I get an uplift from making my mind do what I want it to - making my body do what I want it to.
"It instils an ability to shrug off inclement weather and to plod on regardless.
"There is a moment after my swim when I am completely impervious to any weather and I can just stand and enjoy the awesome view for minutes.
WINTER SEA SWIMS IN WALES
Porthcawl (Christmas Day)
Pembrey (Boxing Day, 26 December)
Tenby (Boxing Day)
Criccieth (Boxing Day)
Saundersfoot (New Year's Day)
"Whether it's physiological or psychological or both, sitting on the bus going back, I feel completely relaxed and content."
There are a small number of others he regularly sees in the water, but the fact that the beach is quiet or even deserted just adds to his enjoyment.
"The ambience is much better," he adds.
He readily admits that some view such a regime as bordering on the eccentric.
"You sometimes see people pointing. If they talk to you it's the same question - is it cold?"
Apart from the obvious exercise, he also confesses that he is not aware of any other health benefits.
But further west, in Llanelli, Charlie Budd is convinced his regular swim is behind his claim never to have suffered a cold.
Charlie Budd has swum off the Llanelli coast for more than 70 years
Now 82, he gives it a miss on really chilly days, but has been a regular swimmer on Llanelli beach since he was boy.
"I used to go swimming in the docks most days - we would always meet up on Christmas Day," he said.
"I still go swimming at the beach."
There he is sometimes joined by a few friends - most in their 60s and 70s.
Charlie, who played rugby league for Llanelli in the late 1940s, said it was regular exercise that kept him in fine fettle.
"I've been very lucky," he said. "I still cycle. I will be at Cefn Sidan for the Walrus Dip on Boxing Day."
That annual fund-raising event has been a family affair since it first started and Charlie is always joined by his daughters and grandchildren.