Imagine being on a boat, floating through the Netherlands with windmills dotting the landscape just beyond your shipboard cabin window. Or enjoying an informal dinner outside on the top deck while drifting past a panoramic and continually changing view of the German countryside. A castle dating to the 1400s slowly comes into view, nestled into the hillside high above a medieval village surrounded by a stone wall. Soon the scene gives way to a parade of steep hillsides blanketed in vineyards.

The experience of floating on rivers through countries in Europe, Asia, Russia and even on the Nile River in Egypt or the Amazon River in South America, is being discovered by a rapidly increasing number of tourists.

Oliver Freytag is the cruise director on the Vili, a 200-passenger, 300-foot longboat of the Viking Cruise Line sailing on a two-week Grand European Cruise from Amsterdam to Budapest on the Rhine, Main and Danube rivers. “Viking began in 1997 with four ships navigating Russian waterways. Today we have 64 boats on rivers around the world,” he says. “In response to the increasing demand we launched 10 boats in 2013, 14 more in 2014 and 8 additional in 2015.”

There are many reasons for the exponential growth. Foremost is a segment of the American and Canadian baby boomer generation made up of 60-plus year-olds that have already traveled extensively.