Whether you’re a Jaws fanatic or just want to live every week like it’s Shark Week, you’ll want to read up on these fascinating facts about sharks, adapted from an episode of The List Show on YouTube.

1. There are more than 500 species of sharks.

They range in size from 8 inches to 40 feet long.

2. The cookie cutter shark grows to up to 22 inches.

The cookie cutter shark uses its suction-cup-like lips to attach itself to prey. Once it’s firmly stuck on there, the shark spins its body, using its bottom row of serrated teeth to take out a cone-shaped chunk of flesh. Typically, cookie cutters feed on sea creatures much bigger than them, but they’ve also taken bites out of a couple of humans … and they’ve been known to leave their mark on submarines, too.

3. Peter Benchley’s 1974 novel Jaws was inspired by a fisherman who caught a 4500-pound behemoth in Montauk in 1964.

The novel wasn’t always going to be called Jaws. Alternate titles included The Stillness in the Water, The Silence of the Deep, Leviathan Rising, and The Jaws of Death.

4. Peter Benchley later became a shark conservationist.

He used his pen to tackle misconceptions about the fish. In 2006, he said, “I could never write that book today. Sharks don’t target human beings and they certainly don’t hold grudges.” Fun fact: Benchley makes a cameo in Steven Spielberg’s 1975 movie adaptation of his novel. He plays a TV news reporter.

5. Shark attacks are very rare.

In 2018, there were 66 confirmed unprovoked attacks. In 2022, there were 57 confirmed, unprovoked bites, five of which were fatal—down from nine fatal attacks in 2021 and 10 in 2020.

In America, the risk of dying from a shark attack is 1 in 3,748,067. You’re more likely to be killed by fireworks, a train crash, or MRSA—that antibiotic-resistant bacteria—than you are by sharks. Worldwide, the risk is even lower.

6. Sharks have been around for a while.

Thanks to their fossilized teeth, we know that they’ve been swimming the seas for at least 400 million years.

7. Some species of shark can live to be incredibly old.

Researchers in 2016 used radiocarbon dating on the eyes of 28 Greenland sharks and determined that one female might have been around 400 years old.

8. Greenland shark meat is a delicacy called hákarl in Iceland.

The shark’s meat is toxic when fresh, so it has to go through a fermentation process that involves burying the shark’s body in sand under rocks for six to 12 weeks. The meat is then cut up and hung to dry. The finished product has a strong scent of ammonia. Anthony Bourdain called it “the single worst, most disgusting and terrible tasting thing” he’d ever eaten.

9. Great white sharks have a man-eating reputation, but they’re much more interested in seals and sea lions.

Great whites have a 40 to 55 percent accuracy rate in catching their seal prey, according to research. The hunting process also often involves the sharks coming fully out of the water, which is called breaching.

10. Great whites are fast.

They can swim at 35 miles per hour for short bursts.

11. Many shark researchers think the theory of “great whites attack humans because they think we’re seals” is a myth.

Great white shark attacks on humans are much less vicious than the way sharks attack prey like seals and sea lions—one study reported that in 76 percent of attacks on surfers, the force would not have stunned a pinniped. In most cases they’re probably just curious—though still potentially deadly. One expert told Discovery that if you do see a shark, the safest thing to do is to remain calm and try to slowly and calmly get back to safety.

12. Great white sharks aren’t found in aquariums—though not for lack of trying.

Since the 1970s, aquarium workers who have tried to keep the sharks in captivity have been having basically the same tragic experience: finding a captive great white shark sick, then dead, within a week. While in enclosures, the sharks can’t swim at the high speeds or over the distances they’re supposed to, so they bump into the glass and get hurt or just stop swimming and die. Younger sharks have tended to do better: The Monterey Bay Aquarium was able to keep a young great white for 198 days, but released her after she started going after other sharks.

13. Tiger sharks and sand tiger sharks aren’t the same.

Another shark you probably won’t see in captivity these days is the tiger shark—not to be confused with the sand tiger shark, which is a completely different species found in aquariums around the world.

14. Female tiger sharks have many, many pups.

After 13 to 16 months of pregnancy, a female might give birth to between 10 and 82 little shark babies. The average is around 30.

15. It’s not unusual for a female shark to give birth to her pups in the place where she herself was born.

One study, which began in 1995 and concluded in 2012, found this to be the case with lemon sharks in the Bahamas.

16. Female mako sharks stay away from male makos.

In research that lasted for four months, a biologist and his team recorded 264 male and 132 female mako sharks in the Easter Island area. They found that there was a clear divide between where males resided versus females. They were baffled as to why. One of them suggested that it might have to do with the fact that males often bite their intended mate, so maybe the females were trying to avoid that whole situation. Fun fact: Biting is often a part of shark copulation, because the males have to hang on to something.

17. It’s not just biologists who have taken an interest in sharks.

In 2002, software programmer Jason Holmberg went scuba diving on vacation and encountered the endangered whale shark. He wanted to make the spotted sharks less mysterious, so he teamed up with an astrophysicist and a marine biologist. They were able to adapt an algorithm that had been created for the Hubble Space Telescope program and use it to start identifying sharks. The algorithm was initially for star mapping, so it made sense as an algorithm for shark spot mapping. They’ve since created a database with 32,000 pictures of whale sharks. The database has helped them track the animals’ locations, which means they can learn more about whale shark life history.

18. The shape of hammerhead sharks’ heads might help with hunting.

Sharks are able to sense electric fields in water, which allows them to determine if they’re in the vicinity of prey. One theory is that hammerhead sharks have more of those sensory organs in their heads, so they can find prey better. Their eyes being so far apart helps too—they have better binocular vision.

19. Shark embryos can sense predators.

In addition to using electric fields to sense prey, sharks also use them to sense predators. Even shark embryos have that ability. In a study published in 2013, a group studying brownbanded bamboo shark embryos found that when the embryos were in the electric field of a predator, their gills would stop moving.

20. Sharks sometimes like to rest in groups.

Nurse sharks and whitetip reef sharks have been observed gathering in groups of two to 40, usually in a safe place like a crevice, often just napping.

21. A basking shark looks very weird when it decomposes.

It quickly loses parts of its jaw and tail. So it’s not unusual for people who spot a decomposing basking shark on the shore to believe that they’ve found a sea monster. This happened in 1970 in Massachusetts.

22. A tiger shark once puked up evidence of a murder.

During the 1930s, a tiger shark at Coogee Aquarium in Australia vomited a human arm, evidence that became part of a murder trial. Thanks to a tattoo on the arm, the person it belonged to, James Smith, was identified. It turned out that he was missing—and the shark hadn’t bitten the arm off, it was cut off with a knife. There was a suspect, Patrick Brady, and a man willing to testify that Brady was responsible. But that witness was shot before the trial. Brady’s lawyer claimed that for a homicide, there needed to be a body and all they had was an arm. Brady went free. The shark unfortunately died.

23. The goblin shark eats using "slingshot feeding."

The deep-sea-dwelling goblin shark has a jaw that shoots outward to grab prey in what scientists have dubbed “slingshot feeding,” so it’s no wonder they often get compared to monsters. The goblin shark can deploy its jaw at 10.1 feet per second—roughly twice the speed that New York City pedestrians walk.

24. The goblin shark is named after a Japanese demon.

Japanese fishermen named the sharks tengu-zame. Tengu is a demon with a long nose that sometimes steals children. And zame means “shark.” That’s how we got our English translation: goblin shark.

25. Not all sharks are ferocious carnivores.

The bonnethead shark has long been observed to eat seagrass—which can account for up to 62.1 percent of its gut content mass. Until recently it was unclear if they were digesting it. But in 2018 it was confirmed through stable isotope analysis that they actually were, making them the first known omnivorous shark.

26. There are multiple species of lantern sharks, including a dwarf lantern shark that doesn’t grow larger than 8 inches.

These sharks have bellies and fins that glow, so it’s thought that when there’s a predator swimming beneath them, the predator doesn’t know the difference between the shark and sunlight filtering into the ocean.

27. Not all sharks are strictly ocean dwellers.

Bull sharks are unusual in that they can tolerate fresh water. Most sharks have to be in salt water because that’s what their bodies can handle—put them in fresh water and they’ll lose too much salt. But bull sharks are better able to retain salt in their bodies, so they can travel in fresh and brackish water. In fact, in 1937, one was caught in Alton, Illinois, 1000 miles up the Mississippi River from the Gulf of Mexico, where you wouldn’t typically expect to encounter a shark.

28. Megalodon sharks were huge—maybe about 50 feet long.

But there are theories that the measly great white shark, at less than half that size, may have caused them to go extinct. It was previously believed that megalodons went extinct around 2.6 million years ago, but when a group of paleontologists and geologists went back through the fossils and data, they pegged it at 3.6 million years ago—which just so happened to be the time that great white sharks were emerging. They were probably able to go head-to-head with younger megalodons and out-compete them for food.

29. Megalodon shark teeth could be around 7 inches long.

And you might want to be on the lookout for them. In 2018, a couple found a fossilized megalodon tooth on a beach in North Carolina. In 2023, a 9-year-old girl unearthed a megalodon tooth bigger than her hand on the shore of Chesapeake Bay in Maryland.

30. An American president had a megalodon tooth.

Thomas Jefferson loved fossils and even kept some on display at the entrance of Monticello. Today, his megalodon tooth is at the Academy of Natural Sciences in Philadelphia. Of course, he signed it.

31. The song “Baby Shark” used to be sung by kids at camps.

Before Pinkfong’s version of “Baby Shark” became one of the most viewed YouTube videos of all time, it was a common song for kids to sing at camps. But when Johnny Only turned it into the bop that we all get stuck in our heads today, he did change some things. In the original lyrics, the sharks attack people and even kill them. Peter Benchley would not approve.

A version of this story was originally published in 2020 and has been updated for 2023.

This article was originally published on www.mentalfloss.com as 31 Fascinating Facts About Sharks.