What is the Bird Bath splash zone at Camden Yards? Why Orioles fans in left field are getting hosed down

Some Orioles fans are leaving the ballpark drenched, voluntarily, after games at Camden Yards.

source https://www.sportingnews.com/us/mlb/news/bird-bath-splash-zone-camden-yards-orioles/sglci11h9h0qr2dxlrao48zc