Stena ferry ships
Essex - Harwich, England
The ferry crossing to the Hook of Holland takes 8hrs and foot passenger £36 (one way).
11/16/18: Stena Line confirm there is a machine on both Stena Hollandica and Stena Britannica. Both are ferries on the Harwich to Hook of Holland route. It's not known (yet) if the coin design is the same on both machines or different.