Iwanci

According to the Jivaro people of the Amazon region in the Ecuador area, the Iwanci is huge serpentine monsters that appear could appear in the shape of frightening Macanci. This is a type of water snake, or as the all-embracing Pani or Anaconda. Whatever form they take, these monsters are unfriendly to humanity and devour anybody that encounters them.

John and Caitlin Matthews, The Element Encyclopaedia of Magical Creatures, 2013, Iwanci, p 255