To capture motion is just really to slow the shutter. But then you have to consider the other factors of your exposure; ISO and F-stop. When I meter to the mid-tone I got 1/30th of a second which really could not capture the motion of the waves. Capturing motion and freezing motion are two different things. You see photos where they freeze the waves; they use high shutter speed for that.
I slapped an old 3-stop ND filter to my lens and now I get 1/4 seconds according to my NDTimer app. 1/4 second is good enough to capture the wave motion. Why can’t I just decrease the F-stop to F/22 to slow the shutter? Diffraction.. its real and F/18 is all I could give.
I usually don’t use filters anymore but it was in my pocket and this was a different situation.
Photographed is Beavertail Lighthouse, Jamestown, RI, USA.