Ampullae of Lorenzini

Every muscle contraction, every heartbeat, every nerve impulse generates a tiny electric field. Sharks can detect fields as weak as 5 nanovolts per centimeter - roughly the strength of a AA battery connected across the Atlantic Ocean. This sixth sense lets them find prey hidden in sand, sense magnetic fields for navigation, and hunt in total darkness.

Small pores on the snout and jaw open into jelly-filled canals ending in bulbous ampullae lined with sensory cells. The jelly has one of the highest known biological conductivities.

Great white sharks can detect the electric field of a single flatfish buried in the sand from over a meter away - even before their eyes ever spot it.