Most dangerous fish

The electric eel (Electrophorus electricus) is an elongated South American fish that produces a powerful electric shock to stun its prey, usually other fish. Long, cylindrical, scaleless, and usually gray-brown (sometimes with a red underside), the electric eel can grow to 2.75 meters (9 feet) and weigh 22 kg (48.5 pounds). The tail region constitutes about four-fifths of the electric eel’s total length, which is bordered along the underside by an undulating anal fin that is used to propel the fish.  The electric eel is one of the principal aquatic predators of the whitewater flooded forest known as varzea. In one fish survey of a typical varzea, electric eels made up more than 70 percent of the fish biomass. The electric eel is a sluggish creature that prefers slow-moving fresh water, where it surfaces every few minutes to gulp air. The mouth of the electric eel is rich with blood vessels that allow it to use the mouth as a lung. 

The tail region contains the electric organs, which are derived from muscle tissue enervated by spinal nerves, and discharges 300–650 volts—a charge powerful enough to jolt humans. These organs may also be used to help the creature navigate and to communicate with other electric eels.