Blue-spotted Stingray (Taeniura lymma) found in shallow waters throughout Papua New Guinea. Its tail is venomous but usually isn't deadly unless whips the chest or any central blood veins. One example would be Mr. Steve Erwin (late). The photo below was taken at Nuakata Island, Milne Bay Province, Papua New Guinea..

Blue-spotted Stingray - Taeniura lymma