For those who like the idea of combining a cycling holiday with a pleasure cruise (and maybe can't afford the Santana version in a luxury hotel boat :o) I've just produced a blog post about pleasure boats on the Firth of Clyde (the classic paddle steamer Waverley) and the Moselle (alongside the Moselle Cycle Route).
It includes schedules of boat services for both area and some basic information about mileages and services on the Moselle route with additional information links for both.
For Tandemists big boats are great as they are much easier to deal with than trains and we had a great trip into Argyllshire on the Waverley with our Pino a while back. As well as being fun they are a good way to extend your reach on a bike tour. We are thinking about the Moselle because we like to take our little caravan so connecting boats allow you a longer out and back trip from your temporary base without cycling in both directions.
best wishes from Sunny Sheffield
Chris