Long exposure during the day is a bit harder but doable. I use a 10 stop ND filter. Put the filter on the lens, set the ISO as low as you camera will allow, go to bulb setting, and mount the camera on a sturdy tripod. A cable release is also handy so your finger isn’t holding down the shutter and causing movement. The amount of time the shutter is open depends on the effect you want to create and the amount of natural light available. On a bright sunny day your time is less than if it’s cloudy. The longer you can have the shutter open the smoother the water gets. That’s why first light or twilight work very well. Also cloudy or stormy days are good for long exposure.
john ferebee photo 
can you share some info on this photo, I’m still trying to figure out long exposures during the day time.
Long exposure during the day is a bit harder but doable. I use a 10 stop ND filter. Put the filter on the lens, set the ISO as low as you camera will allow, go to bulb setting, and mount the camera on a sturdy tripod. A cable release is also handy so your finger isn’t holding down the shutter and causing movement. The amount of time the shutter is open depends on the effect you want to create and the amount of natural light available. On a bright sunny day your time is less than if it’s cloudy. The longer you can have the shutter open the smoother the water gets. That’s why first light or twilight work very well. Also cloudy or stormy days are good for long exposure.
great info & tutorial. ND filter here I come.