Actually, I think if you book both an Amazon river tour, a trekking tour, jeep tour, etc; you'll get a better chance to see the Amazon river animals. My boyfriend and I visited the Amazon on a 5day/4night package through Gero Tours, who we chose after doing a fair amount of online research, and we it certainly met (and often times exceeded) our expectations. With an Amazon vacation package, you'll be doing anything from caiman watching, piranha fishing, nature walks, medicinal talks and tribal visits. And, you can even get to swing on a Tarzan vine. Make sure you do go with a reputable company to guarantee knowledgeable guides who will know perfect English and will be able to teach the names of every plant, animal or insect you may ask about.