Eels aren't the only creatures that can deliver a painful zap of electricity. In fact, not all of them are even marine animals. Here are some others.
Deep-sea microbes: At the bottom of the ocean, these "living batteries" move electrons across the metals on which they live.
Oriental hornet: Brown pigments in the hornet's exoskeleton trap sunlight, while its yellow tissues convert the sunlight into electricity. No one knows why.
Elephantnose fish: Signals travel down the fish's spinal nerves and excite electric cells near its tail, creating an electrical field that the fish uses for navigation.
Electric catfish: The fish can generate enough electricity to power a computer for an hour; it stuns prey with its shock.