The photo at right was shot with the Nikon Coolpix P610 with a Neutral Density (ND) filter that required a 10 f-stop increase in exposure. The camera was mounted on a tripod and the exposure was first measured with the camera for proper exposure without the ND filter and was framed and focused in manual mode. The filter was then screwed on and manual exposure was adjusted for the 10 f-stop difference which ended up to be f-7.6 at 8 seconds. The scene was shot and the long exposure time makes the waves very smooth.
Because the ND filter was mounted on an adapter, the corners are vignetted. That could be taken out by cropping the final photo or just by cloning nearby colors and blending. You could get a similar result by shooting the scene on a night when you had a bright moon. You would have to experiment, but would probably be able to get an 8 second exposure with a full moon.
The photo below is a panorama of 5 frames which were shot in the same way, however with a Nikon D7000. Same procedure was used. The reason measurement of light and focus is done without the ND filter is that there is so little light through the filter that the camera can’t measure or focus.