Some have a tapetum lucidum, a mirrorlike layer under the retina that reflects incoming light and increases the amount of light available to the eye. Sharks do have ears, but the role of hearing in the shark's location of prey is not well understood. A shark can detect sound waves and disturbances in the water with its lateral line, or lateralis, system. This is a series of thin canals, filled with water, that runs along the animal's side. The canals are attached to nerves that send signals to the shark's brain.
Sharks can also sense electric and magnetic fields.
Sensory pores located on the shark's head can detect a prey's bioelectric field even if the prey is buried in sand. A shark can also detect the Earth's magnetic field. Open-ocean sharks may use this information to navigate and orient themselves. Sharks' diets vary considerably and may include plankton, clams, crabs, sea turtles, fishes, seals, porpoises, and whales. Whale sharks and basking sharks strain plankton from the sea through modified gill rakers.