Some species of torpedo ray can $#@% your day up - they can output enough voltage to really do some damage - from wikipedia:
"he main nerves branch repeatedly then attach to the lower side of each plate in the batteries, which are composed of hexagonal columns, in honeycomb formation: each column consists of 140 to half a million gelatinous plates. In marine fish, these batteries are connected as a parallel circuit where freshwater batteries are found in series, transmitting discharges of higher voltage, as fresh water cannot conduct electricity as well as salt water. It is with such a battery that an average electric ray may electrocute larger prey with a current of up to 30 Amperes and a voltage of 50 to 200 Volts, a similar effect to dropping a powered hair dryer into a bathtub."
"he main nerves branch repeatedly then attach to the lower side of each plate in the batteries, which are composed of hexagonal columns, in honeycomb formation: each column consists of 140 to half a million gelatinous plates. In marine fish, these batteries are connected as a parallel circuit where freshwater batteries are found in series, transmitting discharges of higher voltage, as fresh water cannot conduct electricity as well as salt water. It is with such a battery that an average electric ray may electrocute larger prey with a current of up to 30 Amperes and a voltage of 50 to 200 Volts, a similar effect to dropping a powered hair dryer into a bathtub."