How long exposure and, I guess, with a polarizing
filter ?
I am also wondering how you took these long-exposure images.
Without a clear answer from the maker, I am guessing he used a technique called "mean stacking" in photoshop. For this you need several pictures taken of the same scene. In Photoshop you stack them and using one of the stacking options, Photoshop will create an "average" image. This technique mimics a long exposure, but it is fundamentally not the same. If you look closely at the image, you will see "bands" of waves, not a continuous flow. This is what you get when you take (I am guessing) three pictures in rapid succession and stack them.His signature says he has the PolarPro Cinema series of filters. So yeah, probably used the ND16 here.