Reports of giant anacondas date back as far as the discovery of South America when sightings of anacondas upwards of 50 meters (150 feet) began to circulate amongst colonists and the topic has been a subject of debate ever since among cryptozoologists and zoologists.
Anacondas can grow to sizes of 6 metres (20 ft) and beyond,and 150 kilograms (23 stone or approx, 330 lbs.) in weight. Although some python species can grow longer, the anaconda, particularly the Green Anaconda, is the second heaviest and largest in terms of diameter of all snakes, and it is the second biggest extant snake in the world right behind the Reticulated Python. . The lengthiest reputably-measured and confirmed anacondas are about 7.5 meters (25 feet) long. Lengths of 50-60 feet have been reported for this species but such extremes lack verification and too add lack of large prey to support a super-large snake. The two only real reliable claims that can be found describe measured anacondas ranging from 26-32 feet although these remain unverified.
The first recorded sightings of giant anacondas were from the time of the discovery of South America, when early European explorers entered the dense jungles there and claimed to have seen giant snakes measuring up to 18 metres (59 ft) long. Natives also reported seeing anacondas upwards of 10.5 metres (34 ft) to 18 metres (59 ft).Anacondas above 7 metres (23 ft) in length are rare; the Wildlife Conservation Society has, since the early 20th century, offered a large cash reward (currently worth US$50,000) for live delivery of any snake of 9 metres (30 ft) or more in length, but the prize has never been claimed despite the numerous sightings of giant anacondas. In a survey of 780 wild anacondas in Venezuela, the largest captured was 5 metres (16 ft) long, far short of the length required.A specimen measured in 1944 exceeded this size when a petroleum expedition in Colombia claimed to have measured an anaconda which was 11.4 metres (37 ft) in length, but its claim has never been proven. Scientist Vincent Roth also claimed to have shot and killed a 10.3 metres (34 ft) specimen, but like most other claims it lacks sound evidence. Another claim of an extraordinarily large anaconda was made by adventurer Percy Fawcett. During his 1906 expedition, Fawcett wrote that he had shot an anaconda that measured some 19 metres (62 ft) from nose to tail.Once published, Fawcett’s account was widely ridiculed. Decades later, Belgian cryptozoologist Bernard Heuvelmans came to Fawcett's defence, arguing that Fawcett's writing was generally honest and reliable.