Walking the Wall (enigma and revelation)

I am glad the gas service people rang me this morning to see if they could come a week early, because when the service was concluded, the sky became lighter and it had stopped raining. Out I went to Maryport and had a walk, I walked the harbour wall (main image) then I came to an 'enigma'. What was an inspection cover doing on the wall?  (second image).There were no signs of a building near by, no outlets or anything that needed getting to by this means. I carried on with my walk passing the end of the marina, near the marina gates. Several days ago I discovered the marina had a 'beach' that I had not seen since the marina was made. Well today I had a 'revelation' (third image), the vertical gate that is usually raised to keep the water in, was missing.