Sunsets and dolphins in a rain forest

As the world's largest rain forest, the Amazon is a haven for birds, especially parrots. [Photo by Pilar Olivares / Reuters]

In addition to Aqua Expeditions, which operates the 12-suite Aqua and the 16-suite Aria, there is Delfin Amazon Cruise, which also has two small ships (one with only four suites). Our boat had just 24 passengers and a design so chic and minimalist it was once a backdrop in a Conde Nast Traveler fashion spread, with models covered in bangles, scarves and flowing dresses draped on the deck chairs. In contrast, my cruise mates wore lightweight khaki clothing and sensible shoes. They were intent on seeing as much of the rich Amazonian flora and fauna as they could on our four-day trip.

For the most part, my fellow travelers were experienced, passionate, knowledgeable animal lovers and birders, among them a group from Natural Habitat Adventures, a travel partner of the World Wide Fund for Nature. Most were armed with state-of-the-art binoculars and telephoto lenses the size of bazookas. A nature-travel neophyte, I was equipped with an iPhone camera. I soon learned, however, that even the most serious wildlife lover is prone to cruise antics, such as a conga line fueled by pisco, a potent grape brandy.

The excursions offered a strong sense of place. We explored estuaries and were enveloped in the humid rain forest. The sun beat down; we slathered on bug repellent or, alternatively, pulled on ponchos during sudden rainstorms. We visited a local village where we sat in a one-room school in pint-size chairs, listening to the children sing.

Then we returned to the creature comforts of hot showers, air-conditioning, an attentive crew, immaculate housekeeping and nonstop dining on everything from Thai food to local fare like Amazon bass, tiger catfish, Andean trout, ribbons of hearts of palm, and a dizzying amount of camu camu and other local fresh fruits.

Gazing at the water, I saw the familiar elegant arch of a dolphin and the rings it created as it dipped back into the water. Until this trip, I did not even know that such creatures as river dolphins existed. I saw more and more of the fleeting arches.

Andrea Reynolds, an adventure specialist and expedition leader for Natural Habitats, later told me that she was shocked to see so many pink river dolphins. "Cruising on a boat, you know there are things in the scenery you can only imagine," she said. "It was excellent to get out and see the little critters, like insects, tarantulas, the poison frogs, that you don't see floating."

The New York Times