In the December 5th issue of Science, Kenneth Catania of Vanderbilt University published how an electric eel (Electrophorus electricus) uses its shocks to find and catch prey, the details of which were previously unclear given the speed at which an attack occurs.
Red flashes indicate electric pulses. The prey is stunned shortly after the attack starts.
Using a high-speed camera, Catania found that if an eel detects prey, it can unleash a volley of electric pulses which causes its prey's muscles to contract so rapidly (within a few milliseconds) that they lock up, leaving the prey vulnerable and ready to be eaten.
In more complex environments where the prey is hidden and motionless to avoid detection, the eel can emit a few pulses (doublets or triplets) causing the prey to twitch and make its location known. Detecting this movement, the eel then launches its attack volley to stun its prey before eating it.
For more on this, check out this video, the Science article, or Carl Zimmer's New York Times article.