It almost looks like it’s moving under its own steam, but in reality this is of course the very strong tidal current in the Sound of Islay racing past the Black Rocks buoy. Seen from the Islay ferry on a crossing to Port Askaig.
At the southern end of the Sound of Islay on the Jura side the ferry to Port Askaig passes a buoy with the label Black Rocks. The ‘wash’ behind it also nicely show the strong tidal flows in the sound, one of the reasons it was chosen as a site for a tidal power generation installation. Also note the Jura ferry on her way to Port Askaig in the distance.