March 28, 2026, 11:21 am | Read time: 7 minutes
Sharks are fascinating yet feared sea creatures. Movies such as “Jaws,” “Deep Blue Sea,” or “The Reef” have shaped our image of these predators. No wonder many legends and myths surround them. For instance, the belief that sharks must constantly swim or they will suffocate. PETBOOK explored this and other well-known myths by consulting shark expert Dr. Iris Ziegler.
Myth 1: Sharks Mistake Surfers for Seals and Attack Them
One of the most famous myths about sharks is that they attack surfers because they resemble seals on their surfboards. However, this is false, says Dr. Iris Ziegler from the international shark and species conservation organization “Sharkproject.” “Sharks aren’t that ‘dumb,’ and there would only be shark incidents in areas where seals are present.” However, in poor visibility, sharks may not always be sure what they are encountering.
“In case of doubt, they try to find out with a test bite. That means they try to ‘taste’ if it’s edible,” the expert explains. “But they have to bite because their taste buds are located at the back of their palate, not on their tongue—which sharks don’t have!”
Myth 2: Sharks Have No Bones
It’s often said that sharks have no bones, which seems hard to believe when looking at these large predators. But it’s true, as Dr. Ziegler confirms. Like rays, sharks belong to the so-called cartilaginous fish. Their skeletons are made of cartilage, not bone, making them relatively light and flexible.
Myth 3: Sharks Must Always Be in Motion, or They Will Suffocate
Sharks must always be in motion to breathe. According to Ziegler, this is only partially true. “This applies to open-ocean sharks with so-called passive breathing, which need to swim for oxygen-rich water to flow over their gills.” Other shark species have active breathing and can actively push water through their gills while lying on the bottom or hovering, or they can draw in oxygen through a spiracle at the head.
Myth 4: “Shark Attacks” Are Increasing Due to Global Warming
There are recurring myths or rumors that sharks are retreating to more northern waters due to global warming, leading to more attacks in North American coastal areas. However, this claim is “very bold and unproven,” as Ziegler explains. “The fact is that climate change is affecting all marine life, including sharks, as the entire food supply is shifting and decreasing,” the expert says.
Moreover, there aren’t more shark incidents; they are just reported more sensationally. “On average, ten people die annually from a shark incident,” Ziegler clarifies. “This number varies up or down over the years, but the average has been stable for decades and is not higher now.”
Myth 5: The Great White Shark is the Most Dangerous to Humans
Many injuries from encounters between sharks and humans are attributed to the great white shark, often considered the most dangerous. However, this is false, says Dr. Ziegler. “There are only a few shark species that can cause life-threatening injuries to humans due to their size and teeth, including the great white shark.” But it’s not the only one. In fact, there aren’t more incidents with great whites than with bull sharks, oceanic whitetip sharks, or tiger sharks. And there are only about ten incidents per year worldwide with all species.
Also interesting: The Largest Sharks in the World
Myth 6: Sharks Have Regenerating Teeth
Among the myths about sharks, many concern their teeth. There’s talk of an endless number of teeth. If a shark loses a tooth, it is simply replaced—and this is indeed the case, as Ziegler confirms. Over a shark’s lifetime, it can have several tens of thousands of teeth that grow back, she explains. The reason: “Sharks regularly lose their teeth when biting because they are not as firmly anchored in the cartilaginous jaw as the teeth of predators with a bony jaw.”
Myth 7: Shark Skin is So Rough That It Can Cause Injury
If you pet a shark, you can get injured—that’s how rough its skin is. This is also true. “The skin is covered with countless denticles or skin teeth that function like sandpaper,” Ziegler explains. If you touch the skin “against the grain,” the denticles stand up. “And they are razor-sharp,” warns the expert. These denticles are also called placoid scales. Together, they form high, sharp ridges on the skin parallel to the swimming direction. These so-called riblets allow sharks to swim particularly fast.
Myth 8: Sharks Can Smell a Drop of Blood From a Kilometer Away
Among the most famous myths about sharks is the claim that these predators can smell a drop of blood from kilometers away. This is also true, says Ziegler. “Sharks can follow a blood trail like a sniffer dog and even analyze exactly what type of blood it is,” the expert explains.
Fish blood means “Yummy, I’m coming!” for the shark, whereas human blood triggers the following reaction: “I don’t know it, probably doesn’t taste good.” The tale of the wounded castaway attracting hungry sharks and being eaten alive is really just a myth, says Ziegler.
Myth 9: Sharks Lay Eggs
Sharks are fish, and fish lay eggs. However, this only applies to about 50 percent of all shark species, as Ziegler informs. Additionally, only about 30 percent of all species actually lay their eggs in the water, which are then also called mermaid’s purses or egg capsules. “This is mainly done by small shark species like catsharks,” the expert explains.
“Large species like tiger sharks, great white sharks, or mako sharks lay the eggs in the abdominal cavity. There they mature, and the hatched shark babies continue to grow. Once they are large enough, they are born alive.” Many shark species even have a placenta similar to mammals to nourish the small shark babies through the mother’s blood system. This includes reef sharks.
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Myth 10: Sharks Can Glow in the Dark
One of the lesser-known myths is that sharks can glow in the dark. This is even partially true, says Dr. Ziegler. “Especially deep-sea sharks; the reason for this is not yet fully understood.”
Myth 11: During a Shark Attack, You Should Punch the Animals on the Nose to Drive Them Away
Among the persistent myths is the advice to punch sharks in the face to drive them away. However, the expert advises against this! “That means letting the animal get close enough to touch its nose—that’s dangerous.” It’s better to keep the shark at a distance earlier by pushing an object like a camera or swim fins toward it, creating water movement or pressure waves. The shark senses this and moves away.
“If it actually comes to the point where the shark touches you with its snout, you can gently turn the snout away and guide the animal past you,” Ziegler advises. “Punching could trigger panic or aggression… especially since only very few experts master the famous grip to put sharks into a kind of ‘trance.'” If it comes to a “fight” with the animal, you can try to grab the gills. “That’s the most sensitive spot on the animals,” says Ziegler. But be careful! “The shark will interpret this as an attack and will know how to defend itself. So really only use it in an emergency, which shouldn’t happen with proper behavior in the water and during a shark encounter.”