Amadeus draws experiential-minded, well-traveled cruisers in the 50-plus age bracket, with passengers coming mainly from Europe, with a smaller number of North Americans as well as folks from further afield. The line is popular with groups, such as clubs and special interest organizations. It's rare to see families with children onboard. Amadeus is looking to attract younger cruisers with active- and millennial-themed sailings.

Not during the day. Jeans, shorts and casual trousers are acceptable on shore excursions, and comfortable shoes are a must. Amadeus asks passengers to dress "smartly" for dinner, and cruisers do tend to dress up. In general, men wear collared shirts -- some with jackets and ties; dresses, skirts or pants and smarter tops for the ladies. Additionally, for special occasions (such as the weekly captain's gala dinner) the guideline is "semi-formal or smart-casual."

No. Cruise fares do include all meals, wine (a choice of red, white or rose) with lunch and dinner and 24-hour self-serve tea and coffee and late-night snacks. Also included are a once-per-sailing captain's welcome cocktail.

You'll pay extra for drinks at the bar, an optional specialty fine dining experience, Wi-Fi, laundry and any items from the onboard gift shop.

Shore tours or excursions are not included. On all cruises there is an a la carte program of customizable excursion packages, ranging from four shore tours during a weeklong cruise to a package taking in every available tour. Or you can book shore tours individually.

Shore tours -- sometimes two per day -- are available in every port of call and are the most popular activity for Amadeus cruisers. Options might include walking tours with wireless audio guides, bus tours and visits to castles, vineyards and museums along with activities related to specific destinations, such as canal cruises in Amsterdam. In many ports, passengers also choose to borrow bikes to take ashore for scenic bike rides.

Entertainment is livelier than most river cruises with a pair of resident musicians and singers, along with visiting bands and entertaining acts such as sea shanty choirs.

One of the most popular entertainment options, available only on some cruises, is a swashbuckling pirates' night, where staff, and some passengers, dress up and participate in light-hearted music quizzes, treasure hunts and other games.

Best for: Groups, couples and solo travelers looking for an a la carte river cruise vacation with optional excursion program

Not for: Anyone who prefers the freedom of open-seating dining