18mm ZM Distagon, single frame ND1.8, B+W Linear polariser.
This is the Tarawera River, very clear water! Especially considering it\'s source is a waterfall bursting through a wall of solidified lava flow about 60m high... Yes I have a picture of the waterfall, it\'s on the way
Incidentally the nearby town of Kawerau is one of the worst smelling places I have ever been. Lots of intense geothermal activity in the area.