One of the creatures we caught a glimpse of while on the boat headed down river from Manaus was the Pink River Dolphin. The locals call it boto but it has several other names including its scientific name, Inia geoffrensis. Unfortunately the one I saw leaping out of the water was small and quick, and I was unable to get a photo of it.
The Pink River Dolphin likes to hang around near the river bank rather than swim in the center of the river, which makes them accessible to humans. Unfortunately there is evidence that fishermen in the region kill them because the fishermen perceive the dolphin as competition. Apparently the dolphin eats more than 40 different species of fish, along with crabs and other river animals. They are known for arching their neck in interesting directions as they feed among the roots of the flooded forest trees. They are a freshwater species.
When not killed by locals, the Pink River Dolphin can live up to 30 years. However because of pollution, the consequences of river dams and being killed for bait they have been listed as Vulnerable by the 2000 IUCN Red List.
The following is a National Geographic video. I did not take this video footage. http://video.nationalgeographic.com/video/player/kids/animals-pets-kids/mammals-kids/pink-river-dolphin-kids.html
A book from the Los Rios catalog:
Montgomery, Sy. Journey of the Pink Dolphins : An Amazon Quest. New York : Simon & Schuster, 2000.
And some other sources:
And if you are really into it you can "volunteer" with Global Vision International for 2-4 weeks on the Amazon studying the Pink River Dolphin: http://www.gviusa.com/projects/south-america/brazil/volunteer-pink-river-dolphins-project-brazil/home