Stonefish - the world's most venomous fish...

Stonefish Synanceia verrucosa:

The stonefish is the world’s most venomous fish, and its sting is capable of killing a human. Each sharply tipped spine of the dorsal fin has a venom gland at the base from which a duct runs in a groove to the spine tip. Lying quietly on rocks or sediment in the shallows, the stonefish matches its color to its background and is easily stepped on. Its camouflage helps it to ambush passing fish, which are sucked into its cavernous mouth with lightening speed.