When we were in Austria on vacation and there were mountains all around us, and consequently also waterfalls, I tried several times to get this effect of silky water, but nothing worked out (which is also because I couldn't make myself go mountain walking and lugging a tripod around!). So either my attempts to handhold my slower shutter speed photos failed because of camera shake (which was to be expected, but I tried, all the same), or I had to use shorter shutter speeds and thus didn't get water as silky as here!
But the long exposure and the sun at the top didn't work perfectly together here, either, did they?