Alright, let's go over EXACTLY how this image was made.
First, you can see the time and place it was taken, by looking at the photo above. (By the way, I can't really recommend leaving your tripod un-attended like that when it is set up on SAND. The legs of a tripod, unless they have little ski-pole thingies on them, will sink right into the sand as waves wash over them! This also creates a problem with stability, and quite a few pictures were blurred to make this ONE shot... Now you know!)
SHUTTER SPEED: The most important setting is of course the shutter speed. A good shutter speed for blurring things is about 1-30 seconds One second won't blur water very much though, unless it is very fast moving water. 30 seconds however will blur even the stillest of streams etc. This shot was a 30 second exposure, so a wave had time to wash in, wash around the rocks, and the wash back out to sea...
To achieve a slow shutter speed, I need to leverage the two OTHER camera settings in my favor- The camera's sensitivity, (aka ISO) and the lens' aperture. I set my camera's sensitivity as low as it could go, which for this camera is 200. I set the lens' aperture at a relatively "small" setting, f/11 or f/16.
Click HERE to go to the aperture tutorial!
If I had shot with my camera's sensitivity all the way up at 800 or 1600, and if I had "opened up" my lens' aperture to f/2.8 or f/4, I would never have been able to use a 30 sec. shutter speed.