Hydrodynastes gigas is a New World species of large, rear-fanged, colubrid snake endemic to South America. The false water cobra is so named because when the snake is threatened it "hoods" as a true cobra (Naja species) does. However, unlike a true cobra, it does not rear up, but remains in a horizontal position. It is commonly and alternatively known as the false water cobra and the Brazilian smooth snake. No subspecies are currently recognized.