The most feared resident of the Amazon river is not the piranha but the candiru – a vampiric fish only a few centimetres long. It's able to enter a human via any orifice and then swell inside the body, leaving surgery the only option for the unfortunate host!
Opinion remains divided over how the Amazon got its name. Some historians believe it was named after the warrior women (or Amazons) of Greek myth because early Spanish explorers claimed to have spotted tribes of female warriors. Other experts say the word comes from the Native American 'amassona', which means 'boat destroyer'.
The Amazon is the second longest river in the world (just beaten by the Nile) but it's the world's largest river in terms of volume. The mouth can grow to over 300 miles wide and some parts of the river are deeper than the English Channel.
The river rises dramatically during the year, flooding the forest floor and allowing fish to swim between the trees. This has led to the evolution of fruit-eating fish - one kind is tambaqui, a kind of vegetarian piranha which use their powerful teeth to bite into fruit and nuts.
The freshwater Amazon pours out into the Atlantic with so much force that the ocean consists of freshwater more than 100 miles from the mouth. Early sailors were actually able to drink from the sea before South America was even visible on the horizon.
Located near the mouth of the Amazon is an island that was created over centuries purely by the accumulation of the sediment carried by the river current. Marajo Island is about the size of Switzerland and a major tourist attraction.
Over 170 tribes still live in the Amazon rainforest, many of them so isolated that they have almost no contact with the outside world. Experts agree there are probably still some tribes who have never met outsiders.
