Name: Giant Freshwater Stingray US locations: none. Worldwide locations: Southeast Asia and northern Australia Why are they dangerous? Stingrays can pack a powerful punch; they have a barb at the base of their tail that contains deadly poison and a stinger as long as 15 inches. Should I be worried? Freshwater stingrays are hard to see, because they often bury themselves in river sediments. They hunt for clams and crabs by detecting their electric impulses. There are reports of the big animals overturning boats, though they rarely attack people.