Sharks have a very good sense of smell and are sometimes called swimming noses. In a Florida Atlantic University study of the nose responses of sharks and their relatives, the best detection was about one part of scent in a billion parts of water. That is remarkably keen, but no better than the sense of smell of typical bony fishes. Smell also helps sharks find their way in open water. Leopard sharks taken out to sea with their nostrils blocked had trouble finding the way back, while sharks with open nostrils swam in very straight lines toward shore.

Smell can also tell a smooth dogfish which way to turn. In an experiment, researchers gave odor to each nostril separately, with controlled strength and timing. The sharks turned toward the nostril that smelled the odor first, even when the other side received a stronger dose. When the gap between the two sides reached one second, they were no more likely to turn one way than the other.

Sharks hear with ears inside the head, one on each side, and they are most sensitive to low-pitched sounds. Splashing makes low sounds like a struggling fish, and sharks can hear them and may come to investigate. Donald Nelson and Samuel Gruber made synthetic sounds that imitated a struggling fish and played them from an underwater speaker developed by the Navy. In the first tests, 22 sharks came to investigate the fake fish sounds. Hearing can also tell blacktip sharks where a sound is coming from. Free-swimming blacktip sharks dramatically changed direction to move away from low-frequency sounds played from an underwater speaker as far as 74 meters (243 feet) away. Turning away shows that they can tell which direction a distant sound comes from.

Sound is not the only movement in the water that a shark reads. The lateral line is a system of pores and canals that lets a shark sense movement and pressure changes in the water nearby. It picks up vibrations and flow in the water, which helps the shark sense nearby prey. In smooth dogfish, the flow sense also adds to smell. In laboratory tests, sharks of that kind with their lateral line (their flow sense) switched off were badly handicapped at finding where an odor came from, most of all in the dark. For a smooth dogfish, the nose alone is not always enough to lead it to the source: the lateral line helps too.

Sharks can sense the weak electric fields given off by the bodies of living animals, using sensors called ampullae of Lorenzini. These are pores on the head that open onto gel-filled canals, and they are so sensitive that they can detect the electric field of a beating heart. In the early 1960s a scientist named Murray found that the ampullae of Lorenzini in sharks respond to very weak voltages, in the microvolt range. In catsharks and thornback rays, about 1 to 2 microvolts per centimeter was enough to set off strong nerve signals. Experiments by Adrianus Kalmijn and others showed that sharks and skates pick up the electric signals of other fish through tiny pores in the snout. In tests, sharks and rays found prey that was hidden beneath sand or screened from sight, using their electric sense alone. The electric sense works before birth too: when brownbanded bamboo shark embryos still inside their egg cases were exposed to the weak electric field of a simulated predator, they stopped moving their gills, curled their tails around their bodies and froze, as if trying not to be found.

Sharks have sharp eyesight, and their pupils open and close to control the light, as ours do. Many sharks also have a mirror-like layer behind the retina called the tapetum, which helps them see in low light at dusk and night. Researchers examined the eyes of glowing (biofluorescent) catsharks to understand how the sharks see. They found long rods, the light-sensing cells that help the animals see in low light, in the dim blue water where they live. Hammerhead sharks have wide-set eyes: as of November 2026, the winghead shark's two eyes overlap by about 48 degrees in front (a 2009 study), giving it strong depth perception.

Color is a different question. In a study of shark retinas, scientists found no cones in 10 of the species they examined and only a single type of cone in seven others, which together makes 17 species with no cones or only one type (arithmetic: 10 plus 7). With one cone type or none, a shark is unlikely to tell most colors apart. Scientists also looked for the genes for the light-sensing pigments in two wobbegong shark species. They found one gene for the rod pigment and just one for a cone pigment. With only one kind of cone, wobbegongs may be unable to see color.

Researchers in Florida tested a cue that has nothing to do with smell, sound or sight, putting 20 bonnethead sharks in magnetic conditions that matched places hundreds of miles from where the sharks were caught. When the magnetic cues made the sharks seem to be south of where they should be, they began to swim north. In each experiment, what the shark did showed what it could sense: a turn, a freeze, a swim north.

Words to know

• tapetum: eye mirror layer
• ampullae: electric-sensing pores
• lateral: along the side
• microvolt: tiny voltage unit