Hydrodynastes gigas is a New World species of large, rear-fanged, dipsadidae snake endemic to South America. It is commonly and alternatively known as the false water cobra and the Brazilian smooth snake. The false water cobra is so named because when the snake is threatened it "hoods" as a true cobra (Naja species) does. Unlike a true cobra, though, it does not rear up, but remains in a horizontal position. (Wikipedia)