Six sea swimmers are due to attempt the North Channel swim, without wet suits, on Friday.
If successful it will be an historic sea swimming record as the North Channel swim from Ireland to Scotland has never been done in winter.
The Walrus Swim Team met during the pandemic as gyms and pools were closed and they were looking for a challenge.
Given the arduous conditions and water temperatures, the North Channel challenge normally takes place in the summer months.
However the team - whose members are Niamh McCarthy, Declan Bradshaw, Vincent Donegan, Ger Kennedy, Colm Morris and Dave Berry - hope to complete it on 14 January.
All of them have a lot of experience in cold temperatures and have been planning for the challenge since last summer.
They are all based in Dublin and met at the Forty Foot last year and swim there as well as off Killiney and Portrane.
The North Channel swim is considered the toughest of the seven ocean sea swims, which include the English Channel between England and France and the Cook Strait between North and South Islands in New Zealand.
Sea temperatures are expected to be from around 8C to 9C and air temperatures are expected to be from around 2C to 7C across the swim, which should take 15 hours to complete.
The swim is east to west, but the tidal flow is north/south which also complicates it.
The starting point on Friday is from Donaghadee in Co Down to Portpatrick in Scotland and it is being governed by the Irish long distance swimming association, who have placed strict medical conditions on all swimmers in order to participate in the swim.
The swim is raising funds for the Gavin Glynn Foundation which supports families fighting childhood cancer.