For a group of hardy Berliners, Christmas Day is a time to sing seasonal songs, don festive wear -- and take a plunge in a cold lake.

Dozens of swimmers from the Berlin Seals club came to the German capital's Oranke lake Thursday for their annual Christmas dip, complete with red Christmas hats.

The air was relatively mild this year at around 41 F but still bracing enough for the swimmers to warm up by singing Christmas carols before taking the plunge.

Swimmer Beate Korehnke said: "The best is the feeling afterward. There is prickling all over the body -- it's like a sauna but backward."