One of the things I enjoy most about river cruising, aside from the convenience and wonderful ports of call, is that it gives me the chance to see a wide variety of river cruise vessels up-close. And on my recent voyage aboard Viking River Cruises’ Viking Freya along the Danube , I saw vastly more ships than I did a year ago at the same time.

The conclusion that can be drawn from that should surprise no one: River cruising is hot.

What was surprising to me, though, was that all the ships I were nearly brand new. The latest and greatest have been deployed along the waterways of Europe this December, and it is a trend that will only become more noticeable as we move into 2013.

European river cruise ships are dramatically restricted in terms of their height, length, width and draft. Because of that, the playing field — at least physically — is a lot more level in the river cruise world than, say, the deep-ocean market, where cruise lines are free to out-build each other. Even so, it is amazing just how much river cruise lines have been able to vary their products.

AmaWaterways’ AmaCerto, for example, is particularly striking. She has a redesigned, knife-like bow that sweeps back elegantly on her superstructure. Bold letters proclaiming this ship is the “AMACERTO” stand proudly in silver against the royal-blue color of her upper deck, and the ship’s two-tone blue and white paint scheme is recognizable from afar.

Ditto for Avalon Waterways’ Avalon Visionary. All of Avalon’s ships can be easily identified thanks to their attractive blue hulls and proud white lettering on their bows. But what impressed me about this ship as I passed by during a stop in Regensburg, Germany, was that the beds in each stateroom have been rotated to face the large, panoramic windows that fully open to create a giant, open-air balcony-within-a-room. It’s a deceptively simple, yet remarkably clever, concept.

Tauck’s Swiss Jewel and the newer Treasures, on the other hand, have a wonderful old-world elegance about them. But their superstructures are sleek and rounded; even their Navigation Bridges feature curving, dark-tinted glass that makes these vessels, operated by Scylla Shipping exclusively for Tauck, some of the sleekest on the water. But a glimpse inside their windows reveals an inviting world of dark woods, polished brass, and decorative light sconces.

Then there are the Viking Longships themselves, which represent some of the most radical departures from the typical European river cruise ship form, both in terms of physical structure and onboard amenities.

One thing is for certain: With the newbuild market heating up along the waterways of Europe, 2013 is poised to be one of the most exciting years in the history of river cruising.