Sharks are not blind: their eyes carry a cornea, an iris, a spherical lens and a retina, and many species see better in dim water than we do thanks to a mirror-like layer behind the retina.
Colour is the part that does not hold up. Microspectrophotometry on seventeen shark species found cones in only ten of them, and in every one of those a single cone type, which is the signature of an animal that sees the world in shades of one colour. Rays and chimaeras, their closest relatives, carry several cone types. Sharks appear to have traded colour for contrast.
- Cone types found in shark retinasOne, in every species tested
- Binocular overlap, winghead shark48°, against about 11° in a lemon shark
- Sharks with a third eyelidRequiem sharks and hammerheads, not great whites
On this page
How a shark's eye is built
The layout is familiar. Light passes through a cornea, an adjustable iris and a lens, and lands on a retina lined with photoreceptors. The differences are in the details, and each one is a response to water rather than air.
The lens is spherical and rigid instead of flattened and squeezable, which is standard for fish because water and the cornea share almost the same refractive index and the lens has to do all the bending on its own. A shark focuses by shifting that lens backwards and forwards rather than changing its shape. Pupils vary far more than people expect: round in some species, a vertical slit in others, and in a few a horizontal bar.
Behind the retina sits the piece that matters most. The tapetum lucidum is a layer of guanine crystal plates that reflects light back through the photoreceptors, giving every photon a second chance and producing the eyeshine visible when a torch catches a shark at night. In several species, including the blue shark, pigment cells migrate over those plates in bright water and slide back at dusk, so the eye adjusts to the light level over hours rather than seconds. The rest of the sensory kit is covered in shark anatomy.
Do sharks have eyelids?
They do, and this is where two different answers get mixed up. Sharks have upper and lower eyelids like other vertebrates, but those lids barely move and do not blink, because an eye already bathed in seawater has nothing to keep moist. Their job is structural rather than functional.
What some sharks have on top of that is a third eyelid, the nictitating membrane: a tough, opaque fold that sweeps up across the eye from below. It belongs to the order Carcharhiniformes, which covers the requiem sharks, the catsharks and the hammerheads, and it closes at the moment of a bite or when anything comes too near the face. A shark using it is briefly blind on purpose.
The mackerel sharks lack the membrane entirely and solve the same problem differently. A great white rolls its eyeball backwards into the socket as its jaws close, which is why so many photographs of a feeding white shark show a white, apparently sightless eye. In both cases the animal finishes the strike without looking, steering on the electrical signals its ampullae of Lorenzini are picking up from living muscle.
What a shark can see around it
Eyes set on the sides of the head buy width at the cost of depth perception. Most sharks see almost all the way around themselves with a blind spot directly in front of the snout and another behind the head, and only a narrow wedge where the two fields overlap and distance can be judged.
Hammerheads changed the arithmetic by moving the eyes to the ends of a flattened head. Measurements published in 2009 put the frontal binocular overlap of the winghead shark, which has the widest head of the family, at 48 degrees, against roughly 11 degrees in a lemon shark. The great hammerhead sits between the two. The same work found that swinging the head from side to side while swimming sweeps the fields across each other, and that in the vertical plane a hammerhead's coverage is effectively complete.
That is where the 360-degree claim comes from, and it needs the qualification to be true. A hammerhead is not seeing everywhere at once; it is scanning, and the head shape plus the yaw of ordinary swimming fills in what a fixed pair of eyes would miss.
Are sharks colour blind?
Colour vision needs at least two cone types with different peak sensitivities, so the brain has something to compare. One type on its own produces a monochrome image no matter how many cells there are.
A study published in 2011 measured the visual pigments in the retinas of seventeen shark species using microspectrophotometry. Cones turned up in ten of them, and every single one had just one cone type, tuned to the blue-green wavelengths that travel furthest through seawater. The remaining seven had rods alone. On that evidence, sharks are cone monochromats and see no colour at all.
The comparison that makes this striking is with their own relatives. Rays and chimaeras have been shown to carry multiple cone types and can discriminate wavelengths, so colour blindness is not a cartilaginous-fish trait — it looks like something the shark lineage gave up. What it gained is a retina dominated by rods, which is far better at picking out a dark silhouette against a bright surface. That is also why the shade of a wetsuit matters less than its contrast, and why the high-visibility yellow once nicknamed yum-yum yellow is a contrast problem rather than a colour one.
Cones are the cells that make colour possible, and shark retinas carry very few of them. 
In blue-green water, contrast carries more information than hue, which is the trade the shark retina has made.
Which sharks really are close to blind
One species earns the description, and it is not one anybody swims with. Most Greenland sharks carry a parasitic copepod, Ommatokoita elegans, anchored into the cornea of each eye. It scars the tissue and leaves the animal with little usable sight, and the shark appears entirely unbothered: it hunts in near-freezing Arctic water hundreds of metres down, where vision would earn very little anyway.
At the other end, eye size tracks the light available. The bigeye thresher has enormous eyes set in sockets that extend onto the top of the head, angled upward to catch prey silhouetted against the surface from deep below. Deep-water sharks generally invest in larger pupils and denser rod layers, while reef species that hunt by day keep more modest eyes and rely on contrast.
The realistic summary is that vision is a mid-range sense in a stack. Smell starts the investigation but only travels downstream, as how far can sharks smell blood explains; the lateral line reads pressure at a distance; eyes take over from a few metres out and work well at dawn and dusk, which is when many species feed, a habit covered under nocturnal. Electroreception closes the last half metre. Across the species list, the balance between those channels shifts with depth and diet, but none of them is a blind animal feeling its way.
Frequently asked questions
Are sharks blind?
No. Sharks have well-developed eyes with a cornea, iris, spherical lens and retina, and a reflective layer called the tapetum lucidum that improves vision in dim water. Their eyesight is a working sense used from a few metres out, though it takes over from smell and pressure detection rather than leading the hunt.
Can sharks see colour?
The evidence says no. A 2011 study of seventeen species found cones in only ten of them, and in each case a single cone type tuned to blue-green light. Colour vision needs at least two types to compare, so sharks appear to be cone monochromats, unlike rays and chimaeras, which do have several cone types.
Do sharks have eyelids?
Yes, upper and lower ones, though they hardly move and never blink, since an eye sitting in seawater does not need moistening. Requiem sharks, catsharks and hammerheads also have a third eyelid, the nictitating membrane, which sweeps up over the eye at the moment of a bite.
How do great white sharks protect their eyes?
By rolling them backwards. Great whites and the other mackerel sharks have no nictitating membrane, so as the jaws close the eyeball rotates into the socket and the exposed white sclera shows instead. The shark completes the strike without sight, guided by electroreception rather than by what it can see.
Can sharks see at night?
Many see well in very low light. Their retinas are dominated by rod cells, and the tapetum lucidum behind the retina reflects light back through those cells so each photon gets counted twice. Some species also shift pigment over the layer in bright water and withdraw it at dusk, adjusting the eye to the conditions.
Which shark has 360 degree vision?
Hammerheads come closest, and the claim needs a qualification. Their eyes sit at the ends of a wide head, which gives complete coverage in the vertical plane, and the side-to-side head swing of normal swimming sweeps the visual fields across the gaps. The winghead shark has the widest head and the best frontal overlap.
Is any shark actually blind?
The Greenland shark comes closest. A parasitic copepod, Ommatokoita elegans, attaches to the cornea of most individuals and scars it, leaving the animal with little useful sight. It lives in near-freezing water hundreds of metres down, hunts successfully regardless, and is the longest-lived vertebrate known.
Does the colour of a wetsuit attract sharks?
Contrast matters more than colour, because a shark appears to see in monochrome. A strong light-dark boundary, shiny jewellery or an uneven silhouette is more noticeable than any particular hue. The old advice about high-visibility yellow is really about how sharply an object stands out against the water behind it.
References
A small team focused on researching sharks and making marine biology easy to understand. Every page is reviewed against current species records and the SharkSider attack database, and updated when new incidents or research appear.
Published January 22, 2023 · Last updated September 23, 2026 · Filed under FAQ.
