The ferry I didn't know I had!
I spent a long time looking at some slides we took at the end of a 7 week camping trip around Europe after university in 1974. I knew we'd returned to Britain on the ferry from Ostend, but I just could not reconcile the photos, obviously taken from a boat, with the Ostend waterfront. After much use of Google's image search, maps, and street view my search area finally expanded and it became clear this was not Ostend, but Vlissingen, and the memories started coming back to me.
On our last day before taking the ferry home we left Amsterdam heading for Ostend, but instead of the direct route we opted for the more scenic. This involved working our way through the islands that form the end of the Rhine delta. Bridges and causeways got us as far as Vlissingen (Flushing to the English), but to continue to Breskens and on to Ostend we had to use a ferry to cross the river Scheldt, the short but important river that serves the port of Antwerp.
We were lucky to be able to travel all along the coast above ground (and water)—I remember that as a fun day of driving. In 2003 a 6.6 tunnel, the Westerscheldetunnel, opened and replaced the vehicle ferry, but if you are prepared to leave the car behind the Vlissingen to Breskens ferry still operates a passenger and bike service, the crossing taking 23 minutes.