So I've been asked a few times how I get that silky and shiny look on a landscape image, particularly when water is involved. The major input to make this occur is a long exposure. Longer exposures will blur any motion and the longer the exposure the more the blur.
The best way I know to get a good consistent long exposure is with the use of a Neutral Density (ND) filter. ND filters darken the light entering your camera making the sensor think the ambient light is less that it actually is. To compensate for the darker image the photographer must either open the aperture, increase the ISO, or lower your shutter speed to maintain the proper exposure. In our case we want the longer exposure to blur motion and, particularly for landscapes, we want to control both the aperture for depth of field and the ISO for noise.
So how does this work? ND filters come in different stops. What I mean is that these filters darken the light hitting the camera sensor in F-Stop increments. I have a 2 stop filter, 3 stop filter, and a 10 stop filter.
In the image below I used a 10 stop ND filter. I set my camera on a tripod, set my aperture to F11 and ISO to 100. Then I measured the shutter speed and the result was 1/500 second. So with that shutter speed, and the need to reduce the exposure by 10 stops, I slowed the shutter to 2 seconds. Next, I screwed on the filter. The filter is so dark you can't see anything through the viewfinder with it on, so I had to compose the shot before adding it to the lens. Finally, to reduce camera shake I used a cable release to expose the image. It's also a good idea to close the view finder by placing a piece of gaffers tape over it. Some cameras also have a built-in eye piece shutter that can be closed.
By slowing the shutter speed, any movement became more blurred, or silky. The more this kind of movement is slowed the more glassy it will become for anything that is shiny, such as water. It also smoothed out the clouds so I added back some structure to to give them more definition. Even though the water had some ripples from the slight motion the slow shutter speed gave it a very glassy look.