Traveling the same day as river cruise departure, within Europe.

Think of it this way. Your flight (plus travel time to and from the airports) takes how much time? 5? 6 hours? If anything happens to that (I'm assuming very early morning) departure, what's your plan B? With a distance in excess of 500 km., I don't think I would be that risk tolerant. But YMMV.

cruise departs from Basel at 4:00pm

If the boat departs at 4PM, what time do you have to be on board?

If you miss the boat, where can you catch up to it?

Cursory search reveals the best a train does is 6.5 hrs. Flying is 4.5 hrs and you have to get from airport to boat, so may not be as much a time saving as it appears.

Same day travel would not be my choice. My $0.02

Remember Murphy's Law. If something goes wrong, and you truly miss the boat, what have you lost?. $$$ If you go a day early, and things go wrong, you have time to recover. If you go a day early and things go well, what have you lost? Nothing.

I agree with the above. We have a cruise on May 25 and we are arriving 2 days before on the 23. Not worth the risk to miss the boat. Salzburg will be there long after your cruise for a return trip.

I think it is a low risk that you would run into issues causing serious delays, but working backwards, 4 PM departure, you need to be there? Maybe 2:00 to be safe?, train is ~7 hrs, so leaving Salzburg no later than 7 AM, 6 AM gives you some buffer. All that is a long day, some rushing.

It is doable, some risk, tiring. Personally, I might look for a place a bit closer. Munich gets you a couple hours closer, Stuttgart, Karlsruhe, and Zurich, even Baden-Baden or Freiburg are all options.

Munich only being about two hours from Salzburg still gives you most of the day in Salzburg.

Does the cruise company specify the latest time that you must board? River cruises are much different in boarding than ocean cruises. I would guess that 3:30 would still be o.k. That said, there is enough to do in Basel that I would go a day earlier

Sounds a bit risky, delays can always happen. Do you have a plan B if you should miss it? Luckily there are railways along the Rhine on both sides so catching up with the boat should not be hard.

Spending the last night between Salzburg and Basel is also an option. Munich has been mentioned, but you could also consider e.g. Innsbruck.

And what happens if your flight is cancelled?

specific train connections next Tuesday. Same day of the week as the 21st of May, the timetables change in December 11 so the trains will be very similar but here is a real time example.

The last train which works well is the 7:56 departure on a Railjet to Zurich. It gets to Zurich at 13:20 taking 5h24. You'd have 14 minutes to transfer from platform 10 to 14, plenty of time normally but not enough time to get any food or drink comfortably in the station. Zurich is a dead end station on one level for long distance trains so finding the next train only involves walking to the front of the train, walking in front of a couple of platforms and walking along your next train. The train you'd like to catch is the French TGV to Paris which originates there so it will likely be spotted before you arrive and sitting waiting for you. Then 54 minutes on that train and you will arrive at Basel SBB station at 14:28. Total time is 6h32. Is that enough time to get to the ship?

The first train goes through some nice landscapes and calls at Kufstein, Wörgl Hbf, Innsbruck Hbf, Ötztal, Landeck-Zams, St. Anton am Arlberg, Bludenz, Feldkirch and Buchs SG.

If that is too tight the same journey can be done 2 hours earlier - 5:56 to 12:28.

If the connection in Zurich is missed, there is a frequent service from Zurich to Basel SBB, taking 54 minutes at xx:34 and xx:59 and taking just over an hour at xx:36 and xx:08.

How is your tolerance for stress and risk? Different people have different tolerances..

Too risky for me. Go in at least a day early. If you miss the departure, you will need to figure out how to get yourself to the next place the river cruise "ship" docks, so you can board there. I would not want to spend my first day trying to figure that out.

Rather than working it out on the day I would have a pre written back up plan as to how to get from Basel to the next port, and also have the ship's 'phone number ready in case of problems. This is a river cruise, not ocean- you may be able to get them to hold if they know where you are.