...but, why are they called baptistries?
It sounds like these folks are getting baptized. But, we have only one baptism.
Besides, I have been taught that this is not the thing to do. Hierarchs of various jurisdictions have spoken out against taking a dip in the blessed waters. That it is almost disrespectful...as we use this water in case of emergencies when we cannot partake of Holy Communion, we use this water to bless our sanctuaries and our houses, etc.
Anyway, what's the point? It's just a dip in cold water. One will NOT get cleansed of their sins by diving into the frigid lakes or rivers. This is not the way to salvation.
I'm just saying...
Here's some pics from the BBC.http://www.bbc.co.uk/news/world-europe-12224996