The Amazon is one of the largest, most impenetrable places in the world with thick rainforest, undiscovered tribes (that are quite happy to stay that way, thanks) and more river parasites and potential cures for cancer than you can shake a chainsaw at.
The boats that take you between Peru, Colombia and Brazil are hellish but once you get off the main highway of brown water that makes up the Amazon, you can hold out with small tribes, drink ayahuasca and get jungle fever to your heart’s content.
You can head out from Iquitos in Peru, Leticia in Colombia or Manaus in Brazil and you can hire guides to take you and make introductions or else just cut your own canoe from the jungle and row out. Just watch for the tiny fish that likes to swim up the urethra if you piss in the river…
Of course, much of the Amazon rainforest has been harvested of the big trees, especially anywhere near the river where logging boats have access. To get into the real rainforest feeling you’ll need to stray into the interior but be warned that it’s very easy to get lost in the labyrinth of mangroves and swamps.
Not to mention the malaria, yellow fever, jaguars and crocodiles…. Best find an Indian tribe to keep you safe.