Make the ice ring the evening before your event. Pour water into a bundt pan, add cranberries and freeze. It may bubble up a bit in the freezing process but that's ok.
Assemble the punch. Place the ice ring in your punch bowl by running warm water over the bottom of the bundt pan until the ice loosens. Pour the cranberry, pomegranate, sparkling wine and soda water on top, stir and serve with a punch ladle.