Also, swimming in the Amazon river isn't the best idea. Aside from all the other horrors, they have these:
The candiru, sometimes called the vampire or spiny catfish, is a parasite that swims into other fishes gills, sucks their blood and then retreats to digest. This is the guy that has also been known to swim into peoples urethras. However, human invasion is a one way trip, and the fish end up having to be removed by surgery or slowly decay and passed.