Steve Sherman's photograph of Farmington River is an amazing example of slow water. I saw this on his website quite some time ago. I'm sure he'd be happy to explain how he did it. These are just some of the details he gave with the image. Like I said... amazing! Way to go Steve!

5x7 Deardorrf Camera 210mm Symar S lens. F32 @ 15 minutes. Dev. HC110 Normal....
Look for Farmington River.....
http://steve-sherman.com/newengland_main.htm