Estonians braved the dark and cold waters of the Baltic Sea on Friday (December 11) to set a new world record for the largest winter swimming relay, according to event organisers. Five hundred and five people took part in the challenge, which lasted for nearly five hours and covered a total distance of 12.6 kilometres, with each participant swimming 25 meters. Everyone was welcome – the youngest participant was 9-years-old and the oldest one was over 80. The event was hosted at the former Imperial Russia’s submarine shipyard, in an open-water pool, where the water temperature was around 4 degrees Celsius. Swimmers later relaxed in a hot tube and a mobile sauna. According to organisers, the previous world record was set in Finland by 250 swimmers. Winter swimming, believed to boost the immune system and delay onset of dementia, is becoming increasingly popular in the Baltic and Nordic countries. Organisers estimate that number of winter swimmers in Estonia has tripled this year.