Hydrodynastes gigas

Hydrodynastes gigas is a New World species of large dipsadine snake endemic to South America. It possesses enlarged posterior maxillary teeth associated with Duvernoy's gland secretions. endemic to South America. Common names include false cobra, false water cobra, South American water cobra, and Brazilian smooth snake. It is also sometimes referred to as boipevaçu, ñacaniná or yacaniná, from the Guarani ñakanina ('alert head'), mboi-peba, surucucu-do-pantanal, and víbora ladradora ('barking snake').

A mildly venomous species, the false water cobra is so named because when it is threatened, it "hoods" as a true cobra (genus Naja) does. Unlike a true cobra, however, it does not rear up, but instead remains horizontal. No valid subspecies are currently recognized.