I checked their website, www.k-d.com, but it does not answer these questions.
How likely is it that the ships will be full in the summer high season?
Is it true that you cannot make reservations on normal k-d river trips?
How much in advance can you buy tickets?
Details: We will be using a Eurail Global Pass next summer. I am especially concerned about the Mosel river trips selling out since there is only one ship per day.
The boats have a HUGE capacity.
And I wouldn't be surprised if they added an extra boat to tag along behind if it seemed peak-crowded enough to reach a full load on the primary boat.
"How much in advance can you buy tickets?"
Your passage is free with the global pass - isn't that why you mentioned the pass? If you get the flexipass version, try to cruise on the same day you use the train to arrive or depart from this area - that will save the use of an extra travel day, which the cruise will otherwise cost you.
"Is it true that you cannot make reservations on normal k-d river trips?"
That's right.
"I am especially concerned about the Mosel river trips selling out since there is only one ship per day."
The one-ship-per-day schedule indicates that this is NOT a very popular route - and that's because it's relatively dull by comparison. I'd use the train to head up the Mosel from Koblenz. There are other cruises you can take in an upstream direction from Cochem to Beilstein, Traben-Trarbach, and other towns; in this area the river is very windy and a bit more interesting, generally. The Bullay - Zell - Pünderich - Reil area is especially nice. The cruise from Cochem to Beilstein takes only an hour and is quite nice as well.
The Kolb line runs from Cochem.
"How likely is it that the ships will be full in the summer high season?"
I've never heard of passengers being turned away, but I suppose it's theoretically possible.
And please realize this... KD is far from the only company that offers cruises on the Rhine and Mosel.
I missed a KD boat once because it was full. It was mid-October and one of their boats had broken, so the next one was packed. They stopped but only let a few on. We ended up missing our planned ride that day and got a refund on our ticket. If we had purchased tickets for one of the other lines, we wouldn't have had a problem. Generally, the KD boats are the largest so there is plenty of room (at least in September - October when I have ridden them). I've ridden while on a pass (it's been at least ten years since I traveled with a rail pass). If it's an active day on your pass, simply show it to the guy taking tickets on the boat as you board.
