Organs detect electrical currents: great white shark
 

The snout of a great white shark detects minute electrical currents produced by prey using electrosensitive organs called ampullae of Lorenzini.

   
  "Even sightless, the shark is nevertheless still being guided toward its victim by its sensory armory -- by now the shark's electrical sense is operating. Beneath the skin in its snout are numerous tiny, electrosensitive organs known as ampullae of Lorenzini, each linked to the outside world by an external pore. They detect the minute electrical fields produced by the shark's victim and permit the shark to home in on its prey, and to aim with devastating accuracy its first but generally lethal bite." (Shuker 2001:40)
  Learn more about this functional adaptation.