So a while back I heard about these two guys that claimed to have found a huge snake while out on a scientific expedition to do just that. The snake in question is called a Yacumama (and is prevalent in the lore of the peoples living throughout the Amazon River Basin). This particular
scientific expedition took place in the Peruvian part of the Amazon River Basin. According to the lore, the snake is supposed to reach a length of 40 meters and a diameter of 2 meters! Pretty dang big! Regardless this particular expedition turned out to be a hoax (and I harbor doubts that the Yacumama actually exists quite frankly - but these 'crypto-zoology' stories always fascinate me even if I know they aren't real).
However, while I was rooting around and finding out that it had been found out to be a fraud, I found this attached photo of a rather large Anaconda (of which the Yacumama is supposed to be related) which is not a hoax! You can not see from the photo exactly how big this snake actually is...but you can see that it is almost the same girth as the kayak it is next to and it appears to be longer. I have a kayak similar to the one in the photo and the dimensions of my boat are 12'x28". I've no idea how long the snake in this picture was...but I'd hazard a guess that it is somewhere in the neighborhood of 20" in diameter!
Just for the record; I don't think I'd feel terribly comfortable sitting in that kayak...