That is a tanker not a ferry. The red bit is the pipework and flying bridge along the top of the tanks, and the white bit in the middle is the hose-handling crane which connects the hoses from ashore to the manifolds on the ship when loading and discharging cargo.
A line from the Drop Redoubt through the Eastern Arm runs just south of east and bisects Dunkerque so I would guess that the smoke plume is emanating from the heavy industry in Dunkerque East.
I was a bit disconcerted last trip when we were departing Dunkerque West where the nuclear power station at Gravelines is situated. Sirens started going off consecutively in different parts of the power station. I was minded to tell the Old Man to put the handles down and not to stop until we passed the Azores.
Then I looked at my watch and saw it was noon French time so it was just a test. Bit eerie all the same!
