This is the same set of rocks as in Edge of the World, from the same viewpoint as yesterday. The spots of colour in the distance are the dockyard cranes at Avonmouth, with Portishead on the right.

There's no transparency in this water: it's laden with silt. Picture a mile-wide channel of chocolate milk and you get the idea. With a long exposure, though, the choppy surface blends the rocks into the water but keeps a sense of turbulence. The light patches are patches of foam from the breaking waves.

Tech stuff: I used the ND110 filter here, for an exposure of 20 seconds. I tried doing some long exposures of the waves breaking on the sea wall, too, but there wasn't enough contrast in the scene to make it work.