These are the same animals that killed Steve Irwin. RIP Steve.
Stingrays swim with a "flying" motion, propelled by motion of their large pectoral wings (commonly mistaken as "fins"). Their stinger is a razor-sharp, barbed, or serrated cartilaginous spine which grows from the ray’s whip-like tail (like a fingernail), and can grow as long as 37 cm (about 14.6 inches).
On the underside of the spine are two grooves containing venom-secreting glandular tissue. The entire spine is covered with a thin layer of skin called the integumentary sheath, in which venom is concentrated. This gives them their common name of stingrays, but the name can also be used to refer to any poisonous ray.