Leyend: Moray Eel - Because they lack gills moray eels (Gymnothorax mordax) constantly open and close their mouth in order to breathe. This habit has a tendency to showcase the moray's fang like teeth and has lead to exaggerated fears of a creature that is typically very shy around humans. Apart from their teeth morays eels are also known for their powerful jaws and can get as large as 6 feet!