blown out means that the picture has recorded almost pure white because too much light has hit the sensor and all detail is lost.
You probably just need to study the basics of exposure before you start thinking about how to shoot a particular type of photograph. Because until you understand the basics of exposure you'll just be coming here every time you want a certain shot and asking "how should I set my camera?!" every single time. Once you understand how the basics of exposure work, you can figure out a lot of stuff like the questions you are asking by just applying that knowledge and some basic logic.
Ultimately it all boils down to this:
1) you need X amount of effective light to achieve Y brightness in a given photo. THis is a direct relationship, ie the more effective light, the brighter the photo. Photographers refer to this as the exposure.
2) The amount of light in the environment plus any flash you may use is the first factor to consider. The light in the environment is referred to as the ambient light. For the shot you are referring to above, ambient light is all there is. Obviously the more ambient light there is, the more light there is.
3) The shutter speed controls how long the shutter is open. Obviously the longer it is open, the more ambient light is let in. (this doesn't work for flash, since flash flashes for as long as the flash flashes, the shutter speed doesn't change that until you get to extremely fast speeds). Shutter speed also obviously effects the amount of 'movement' captured in the image. What causes the 'silky' look you want is that the water is moving. So when you capture it for a long time, it creates an averaged out look, which is smooth and silky.
4) the aperture (f/stop) controls the rate at which the light comes into the camera. ie its essentially how large the opening that lets light into the camera is. THe larger the opening, the more light that can pour in, the smaller, the less that can pour in. It also controls how much of your frame is in focus. If the hole is very large (an aperture of f/2, for instance), then the depth that is in focus will be small. If the opening is tiny (f/22 for example) then almost the entire image will appear in focus.
5) The ISO controls how much the light that comes in is amplified (for digital that is, for film it controls how sensitive the film is to light). So if a picture is X bright at ISO 100, its 2X bright at ISO 200. At high values ISO also can cause noise and color desaturation as well.
For the look you want, you want a long shutter speed. You usually need about 45 seconds at least to get even moderately silky water. In daylight, this is a LONG time for a shutter to be open. A normal shutter speed in full daylight at a normal aperture (say f/11) and ISO 100 is something like 1/40 a second. So you're essentially letting in 1,600 times as much light with that shutter speed as you'd normally want. This will mean that even if you go all the way down to f/22 (the smallest most consumer grade lenses will go), way too much light will be entering the camera if your shutter is open for 45 seconds. The water will be smooth, because it wil be completely white, just like everything else in the picture, your picture will come out completely white and all detail will be lost.
Neutral density filters are basically like sunglasses for your camera. Very high quality sunglasses that don't change the color of the light (hence neutral). a 9 stop ND filter basically means you are cutting the amount of light that gets in down by 256 times (each stop is half as much light, thus 1 stop down is 1/2, 2 stops down is 1/4, 3 stops down is 1/8,etc) . Thus allowing you to take a long exposure in the daylight without making your picture pure white.
Your solutions to this problem without a ND filter is basically shoot when it's less bright. Either about 45 minutes after sunset, or 15 minutes after sunset when it's very overcast (this can be a dramatic shot indeed, as you get the rolling clouds as well).
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