Stingray

Stingrays are common in coastal tropical and subtropical waters, but some species are also found in temperate regions. Although they look nothing like fish, having a flat body and one or more barbed stingers on their long tail, they are actually a species of cartilaginous fish related to sharks.
Even though stingray's venom is painful, it is not deadly unless the victim is stung in the chest, but they aren't normally aggressive.
One of the things Stingrays are good at is camouflage. They like to stay on the bottom on the ocean buried in the sand either hiding from predators or waiting for its prey to come.
It is said that in Ancient Greece dentists used the stingray's venom as an anesthetic.