Scorpion fish are a group of rather spiny and often bizarre-looking fish that include several species with defensive venomous fin spines. Wounds from touching the ends of these sharps spines can cause severe pain. Treatment of a wound entails applying an extremely hot poultice for at least 30 minutes to break down the powerful protein toxin.
Scorpion fish are largely solitary bottom-dwelling reef fish that rely on their camouflage to avoid detection while they lie in ambush for small fish. The exceptions are the various species of lionfish, which tend to be free-swimming.
The best defense against scorpion fish is avoidance. Simply control your buoyancy and keep clear of the bottom.