Over 500 swimmers will dive into Dublin's River Liffey today - wearing only swimsuits, goggles and a smile.
The annual challenge is now in its 99th year - with a 2-kilometre course from the Guinness Brewery to the Customs House.
Brian Nolan, is the Chairman of organisers 'Leinster Open Sea' - he says it's the only capital city in Europe to have such a race:
"There's a total of 570 that's 315 men and 220 ladies it starts at Rory O'More bridge finishes at the customs house."
"It kicks off with our lord mayor Nial Ring he sounds the bell at 3 o'clock for the men and 4 o'clock for the ladies."