Eurail Flexipass used for Rhine Cruise?

If your rail pass is activated for that day (i.e. you've filled in that date), it will be valid for the boat and the train. BTW, when filling in the date, in European format - day/month/year - be sure to put a "crossbar" on the seven, to show it is not a one. Otherwise, it will look like you used the pass for a previous date, and you will have to fill in the 7th again. BTW, Bingen to Koblenz is DOWN the river (in the direction of flow).

"I was planning on taking a train from Rothenburg to Bingen, and then taking the Cruise up to Koblenz, and then another train from Koblenz to Bacharach, where I'd spend the night." That will work fine on one flexipass day. But listen up - riding beyond Braubach to Koblenz requires another 50 minutes of cruising; the scenery as you approach Koblenz is somewhat industrial and less than interesting. Once you get to Koblenz, you have a LONG walk to the train station or a bus ride ahead of you. Choices: 1.) Get off the boat in Braubach to visit Marksburg Castle (if it's still open when you get there) - then take the train into Koblenz and change there for Bacharach, or... 2.) Get off the boat in Boppard (across the river and south of Braubach, on the same side as Bacharach) instead. From Boppard, it's only about 20 min. by direct train to Bacharach. By the time you reach Boppard you've already spent 2.5 hours on the boat and already seen almost all of the good scenery. Boppard is a handsome little town too - cool chairlift ride there to a lookout and a great view of the valley. After Boppard you could also stop in St. Goar, the most scenic spot on the whole river, on your way to Bacharach, whichever plan you choose.

Thank you both so much for the information on the cruise as well as the Rhine. I'm so excited. Sincerely,
David