I posted this as much for the phenomenon as for the pic itself. The canal was frozen over and up to the line on the photo, the ice was smooth and intact. The other side of the line it was broken up. No external influences on the canal sides and, being a canal, vitually no current and no wind. Any ideas?
70.0 - 300.0 mm (35 mm equivalent: 113.3 - 485.5 mm)