Night Of Ivan Kupala. Belarus, Russia, Ukraine

The holiday is still enthusiastically celebrated by the younger people of the Eastern Europe. The night preceding the holiday (Tvorila night) is considered the night for "good humour" mischiefs (which sometimes would raise concerns of law enforcement agencies). On Ivan Kupala day itself, children are engaged in water fights and perform pranks mostly involving pouring water over someone.
Folklore and Slavic religious beliefs
Many of the rites related to this holiday within Slavic religious beliefs, due to the ancient Kupala rites, are connected with the role of water in fertility and ritual purification. Youths would jump over the flames of bonfires. Girls would float wreaths of flowers often lit with candles on rivers and would attempt to gain foresight into their relationship fortunes from the flow patterns of the flowers on the river. Men may attempt to capture the wreaths, in the hope of capturing the interest of the woman who floated the wreath.