Step 6; Trees or Sky?
I suppose I could have carried on copying the trees from right to left but I decided I would be happy with a tree-less shore on the left side.
If you look carefully at this clip, you will see I have positioned the Clone Tool over a piece of clear sky. Use of the "Alt" key with the left mouse button loads the Clone Tool with a sample of that piece of sky. Guess where this is going. Correct; down to the shore. By carefully painting along the edge of the shore with this piece of sky, I can gradually build up lots of sky, overwriting the unwanted boats, trees etc.