On the 19th of January The Russian Orthodox festival of Theophany, or the Baptism of Our Lord, is widely celebrated in Russia. Epiphany - a Christian festival celebrated in honor of Jesus' baptism in the Jordan River by John the Baptist. At baptism, according to the Gospels, the Holy Spirit descended on Jesus as a white dove.
On the 19th of January and the night before Orthodox people follow the main tradition, they go bathing in some natural source of water.
So at this day usually the local rivers and lakes are full of the people wishing to commit this ritual, not minding the temperature of the air (about -25C) and of the water(+3C).
Also, many people in Russia believe that the water being picked up at Baptism Day has some sort of magic. It can be kept next 365 days without getting any smell or become rotten. So many people collect the water at that night and keep it at home, drinking it from time to time during all the year.
Girls and young women use the eve of Theophany for guessing their future husbands.