Aria Amazon -- Iquitos, Peru
Body of water: The Ucayali River
Number of rooms: 16
Cost per night: $3,000-$3,300 for a three-day cruise; $7,000-$7,300 for seven
Why stay?: For starters, the amazing wildlife — as in rare pink dolphins, three-toed sloths, toucans, and Taricaya turtles. Built in 2011, the Aria Amazon is a marvel of luxury and rooms feature floor-to-ceiling blackout windows so you can spy all of the aforementioned animals with a pair of binoculars whilst lying in bed. Or, you can soak in the sights (and maybe do a little piranha fishing) from the outdoor lounge and observation deck.