We spent the morning cruising along the Danube. The current has been so strong we were over an hour late getting to Passau. We go through 68 locks on the trip from Budapest to Amsterdam. We were up on the top deck this morning when we went through one of them. As we approached, they had everyone sit down. The bridge over the lock was so low we could actually reach up and touch it. If we had been standing we would have been knocked over. After that the bridges were even lower and they closed the top deck. To get under some of the bridges, they fill ballast tanks on the ship to make it lower in the water. It's the same principle used when submarines dive. We took about a two hour walking tour of Passau which is at the confluence of the Danube and the Inn Rivers. Surprisingly, the Inn is a faster and more powerful river than the Danube - it's just shorter. Our guide, Alex, was from Wales but now lives in Germany. We think he is a frustrated comic - his narrative was hilarious. Not sure how he ended up being a tour guide - he has a Ph.D. in Byzantine history. Guess there is not a big market for that skill set.