In Poland, on the second day of Easter there is an old tradition called Smigus-Dygus. In old days on that day young man tried to flush the water on girls. It was often part of courtship, because man searched for the most popular, beautiful or favorite girl. It was believed, that the girl, which was flushed with water, would have luck in the whole next year. Nowadays ofcourse on Smingus-Dyngus everybody, not only men, are pouring water on each other.
In the old days, on the countryside, man flushed girls with whole bucket of cold water. Polish elite celebrated Smigus-Dygus more gently - they flushed with the cups filled often with warm water.
Śmigus-Dyngus wasn't very popular in the cities, and so it is today. Traditional puring happens more often in villages and small towns rather than big cities.
Battle on water guns in Krakow - watch from 1:20
In some regions, there was also contr-Smigus-Dyngus tradition called Babasik. This was after Smigus-Dyngus day and this was revenge of woman on man for the Dyngus. On Babasik, initiative was in the girls hands. This time they flushed water on man.
On Śmingus-Dyngus even public services are flushing the water (better to watch with music turned off ;-))