Anacondas are four species of aquatic boa inhabiting the swamps and rivers of the dense forests of tropical South America. The Yellow Anaconda can be found as far south as Argentina.There are two possible origins for the word 'anaconda.' It is perhaps an alteration of the Sinhalese word henakandaya, meaning 'whip snake', or alternatively, the Tamil word anaikondran, which means 'elephant killer'.^[1] It is unclear how the name originated so far from the snake's native habitat; it is likely due to its vague similarity to the large Asian pythons. Local names for the anaconda in South America include the Spanish term matatoro, meaning 'bull killer', and the Native American terms sucuri and yakumama. Anacondas as members of the boa family are sometimes called water boas. The Latin name for Anaconda is Eunectes (from the Greek "ευνήκτης", meaning "good swimmer").

There is some debate about the maximum size of anacondas, and there have been unverified claims of enormous snakes alleged to be as long as 30-45m (98.4-147.6ft).According to Lee Krystek ^[2], a 1944 petroleum expedition in Colombia claimed to have measured a 11.43 m (37.5ft) specimen, but this claim is not regarded as reliable; perhaps a more credible report came from scientist Vincent Roth, who claimed to have shot and killed a 10.3m (34ft) anaconda in Guyana.

There are some reports from early European explorers of the South American jungles seeing giant anacondas up to 18.2m (60ft) long, and some of the native peoples have reported seeing anacondas up to 15.2m (50ft) long.^[3], but these reports remain unverified.Another claim of an extraordinary size anaconda was made by adventurer Percy Fawcett. During his 1906 expedition, Fawcett wrote that he had shot an anaconda that measured some 18.9m (62 ft) from nose to tail. ^[4] Once published, Fawcett’s account was widely ridiculed. Decades later, Belgian zoologist Bernard Heuvelmans came to Fawcett's defence, arguing that Fawcett's writing was generally honest and reliable. ^[5]