For some time now, I've been taken with shots like these. I first stumbled on a few photographers doing work like this on flickr over a year ago. So, I headed out to try some long exposure waterscapes. No matter how low my ISO or how stopped down my fstops, I could never achieve what they were doing. I figured they must be shooting in total darkness. Then I discovered neutral density filters. Naive? Sure. Willing to experiment, try things, figure out why they don't work and what others are doing? All the time. I am currently working on a portfolio of these images, so you are certain to see more of these.
If you don't know the work of Michael Kenna or Michael Levin, I encourage you to check out both of them. And if you want to check out some marvelous black and white work on flickr, some of which is long exposure work, I suggest Monochromatic Visions.