"Attention ladies and gentlemen. We are approaching a very low bridge, and we kindly ask that you vacate the sundeck until we have passed." Welcome to river cruising in Europe, where the experience is unlike any other cruise you've likely encountered. Floating down the Moselle River toward Germany's border with Luxembourg and France, we are passing under a bridge that requires not only all tables and deck chairs to be removed from the sundeck but also the side railings and even the captain's pilot house to be lowered so that they are flush with the upper deck. Fortunately, the side railings are hinged, so that they can be folded over onto the deck. The captain's pilot house is designed so that it lowers below deck. With the bridge only 100 yards away, I squeeze my head through a canopy draped over the stairwell to the sundeck, completely flush except for the captain's bald crown poking above the deck from the pilot house. We make it under the bridge, by the way, with only two inches to spare. "The captain has been with us a very long time," says Wilhelm Bahrs, the ship's affable hotel manager. When I don't get the joke, he rubs his head as if to indicate that the low bridges have scraped the captain's noggin too many times. Ah! So that's why he's bald.