This is a town tradition where Im from. Every year to celebrate new years a group of about 20- 30 people uhhh gathered together below a restaurant on the river in the town where Im from. And jump into the water. Its called the polar dip. The restaurant is called the Gateway, not known for any specific foods but its one of the only restaurants open in town. They have hot chocolate and blankets for all the participants who are brave enough to jump in the freezing water. Done at 9am on new years day, not done at the traditional liminal period.
While its never been said what it represents, it looks like a symbolic refreshment or renewal. The informant thinks the tradition is sort of a new baptism where you jump in the water, solidify new years resolutions and begin the year anew.
I agree with my informant’s analysis. This tradition seems like people cleanse themselves of their past sins of the year and start the new year fresh. Although 9am is a unique time point, perhaps it is for practical purposes since most people do not want to jump in freezing water in the middle of the night. Also, new years night traditionally involves champagne, so drinking and swimming may not be the safest combination.