Experiment at night. A ferry from France was entering the harbour. Camera on tripod. Guessed exposure (about 5 seconds) holding shutter open on bulb with a cable release. Very difficult to judge the movement of the ferry.
Thank HiHo. The colour of the tower illumination is accurate. It changes in a sequence and it was on a sort of mauve when I took the picture. Most of the lights on the ship were white. The red lights on the ship are the port (left) side running lights. The green I'm not so sure, though it was a bar or disco or something but couldn't have been on several decks......will have to check next time she's coming in.