How to blur water creating blur in water is easy to do.
Once you have your neutral density filters, sturdy tripod, and a remote shutter release (or 2-second timer), you will be ready to start. Try experimenting with a 2 stop ND, 3 stop ND, etc. Do you want silky water or water with some personality? Start with 1/30 of a second and slower and find a style you love.
Most water can be blurred with a shutter speed longer than 1 second. But to get a good effect depends on how the water is moving. Ocean water will still look choppy if the exposure is shorter than 30 seconds — it sometimes takes exposures that are multiple minutes in length to make a perfectly even blur. The faster the water moves, the less time you’ll need to blur it.
For example, a waterfall can be blurred with a much quicker exposure than ripples on a lake. The best way to find out exactly how long to expose is to take test exposures and then analyze them in the camera.