Day long Cruise out of Koblenz in Late Dec.

Trains leave Koblenz for the south through the scenic part along the east bank (direction Rüdesheim) and along the west bank (direction Bingen.) The Rheinland-Pfalz ticket (daypass, 22€ for 1, 26€ for two) is good for such trips. It will get you up the Mosel from Koblenz to Cochem and Trier as well. Rheinland-Pfalz Ticket

KD cruises run only on demand in the winter months. I wouldn't count on it and wouldn't want to do it even if a cruise did make - there are few eskimos touring the Rhineland, the only folks I know who might find such a cruise enjoyable. Here's the limited schedule in case you're very tough. Call in advance to promise you'll board. A better choice is the train - tracks run along both sides of the river between Mainz and Koblenz on the west bank and Wiesbaden and Koblenz on the east bank. Trains are warm and have windows that provide you similar views. You can take the train to towns that have castle tours - like Braubach: Marksburg Castle is open daily in winter except for certain holidays. St. Goar's Rheinfels (ruined castle) is open weekends, weather permitting.

thank you so much for the quick reply. Can you take the train from Koblenz. What do you suggest is the best station to leave from and return too. Once again. Thank you.

Sorry yes, I see you can take the train from Koblenz. Thanks

Thank you so much Russ.

There are several other cruise companies that operate out of Koblenz besides KD, and at least a few of them operate all year, river conditions allowing. I admit, I never seem to be able to remember their names, but I see them cruising the river all year. Unlike KD, though, they stop infrequently, if at all. If you're in Koblenz, just head down to the waterfront and you'll see them.

Kolb Brothers does day cruises on the Mosel. Unfortunately, they shut down Oct 31 and won't start up again until spring. http://www.moselrundfahrten.de/en/schedules-region.php?filter=Cochem&bereich=Cochem
"Cruising" by train is the way to go in the winter. R-P ticket makes it "hop-on hop-off".

Taking a cruise along the Rhine or Mosel in late Dec woudn't be much fun - in my book. Most likely you'll encounter snow, rain or fog. How about staying one night in an 800 yr old castle in Bacharach? It's a hostel (H.I.) - you might have to share your room with a stranger and you have to set up your bed (they'll give you the bedding). You'll meet other international travellers. The view from your window or the terrace is fantastic (on a clear day). The price is right: from 20.50 Euro/night and that incl a hearty buffet breakfast. Reservation is a must - this castle is extremely popular.
http://www.hihostels.com/dba/hostels-Bacharach-022077.en.htm