Interest and participation has increased hugely in recent years across the country, according to the Outdoor Swimming Society.
Eighty outdoor swims are being held over the 2015 season, with most taking place on Christmas or Boxing Day.
Safety advice has been issued by the society for the first time.
Spokesman Will Cairns said it was expecting more people to take part this year in the sea, rivers and lidos.
"What's interesting this year is the temperature of the water.
"It's three to four degrees higher in certain places than it was this time last year. Temperature does play a part."
He said overall membership numbers increased from 15,000 last year to 25,000 this year and that 40% of members now actively swim throughout the winter.
"The Christmas swims very much appeal to the British psyche of doing something different, something slightly weird and wonderful," he said.
- Do not take part if you are pregnant, suffer from asthma or have a heart condition.
- Get warm before the swim and remove your warm clothing at the last minute.
- Go in feet first, not head first, and control your breathing before immersing your shoulders.
- Have low expectations of how long you will be in for or how far you will go
- Dry off and put on layers within ten minutes of getting out
Charlie Hoskin, 33, from Cornwall, described herself as a "granite-fleshed cold-water bathing enthusiast" who always swims in the sea at Christmas.
"The sensation is truly electrifying. It is a great way to test your constitution and boost your immune system," she said.
Daniel Fox has been photographing the Exmouth Christmas Day swim since 2007.
"Its getting massively busy now and the atmosphere is amazing. Costumes are getting wilder and there are more and more people taking part," he said.
"There are about 1,000 swimmers, thousands of spectators and tens of thousands watch by webcam too so we have a worldwide audience".
Brian Thomas from the Serpentine Swimming Club in London said: "We have seen a huge growth in numbers over the past five years".
He said its Christmas swimming race tradition began in 1864 and about 100 people usually take part after a strict vetting process.
"Swimming in a wetsuit is cheating" he said, although stressed that the club has "strict guidelines" making sure participants have acclimatised.
Christmas swims are expected to attract bumper numbers this year due to milder winter weather and growing popularity for the craze.