A corny title, yes. But this really is an amazing video. It shows electric eels coming out of the water to attack prey (or potential predators). Read on for a more detailed explanation, but if you just watch the video, don't stop with the slo-mo. Continue on to see the attack in real time. Awesome.
Smithsonian and Nature report on this study conducted by Kenneth Catania, a professor of biological sciences at Vanderbilt University and published in the Proceedings of the National Academy of Sciences:
...when Catania dangled conductive materials into his eel tank in the shape of things like human arms or crocodile heads, the knifefish [eels] jumped partly out of the shallow water and attacked, rubbing their heads against the invading object for several seconds.
Meanwhile microphones the biologist had placed inside the tank confirmed the attacks were coordinated with a high voltage volley. "Importantly, they're not just leaping randomly. They're really following the conductor out of the water,” he says. "It's fascinating to me because it's clearly a very impressive and very useful defense mechanism."
He has found that the eels can deliver a more concentrated shock by projecting out of the water and pressing their chins against animals. "The eels may not be very good at shocking something that's not fully in the water so this behavior is the solution,” he says. "The higher [the eel] gets, the more of that power goes through what it's touching and the less goes back through the water from its tail. These eels have evolved to have remarkable output, and it turns out they have evolved pretty remarkable behavior to go along with that."
...his discovery supports a widely disbelieved observation made more than 200 years ago by the Prussian explorer and naturalist Alexander von Humboldt. In a paper published in 1807, von Humboldt recounted that he had seen South American native fishermen herding horses into a pool of electric eels; the eels would discharge themselves against the horses and could be fished safely when they were exhausted.
More at both links.