The Candiru fish is a parasitic catfish which is native to the Amazon basin.
The Candiru fish (Genus: Vandellia, Species: V. cirrhosa) is a small translucent fish which can grow up to 16 inches, but most are much smaller (usually only 1 to 2 inches).
The Candiru fish mostly affects other fish. The candiru is attracted to the ammonia smell which is produced by fishes gills. There are, however, alleged reports of the candiru fish entering the urethra of a person while they are in the water.