With the recent spate of shark sightings in Maine waters, people ask if that will keep me from diving. My reply is that you stand a better chance of getting struck by lightning (four times more likely, actually), but having said that, it doesn’t mean I would run out into a thunderstorm either! Use your judgument and exercise common sense.

First off, at least 21 different kinds of sharks swim off Maine. They are out there, all the time. And then every summer, our waters get visited by the world’s second-largest shark, the giant basking shark. It is slightly smaller than the whale shark.

And every so often, great white sharks appear off the coast as well. They are just a part of the marine world. Once you accept that, then for scuba diving common sense might be to avoid particular areas where there have been recent sightings. Choose alternate sites to dive.

Do not linger long at the surface, like off a boat. In the water column, keep more to shallow water or stay near the bottom, since attacks tend to come from below or in the surf areas. Try to avoid swarming schools of fish — that may indicate seals are hunting the schools and any sharks around might be hunting those seals.

Speaking of sharks, I recently received a piece of one in the mail! I have some North Carolina friends who are big time shipwreck hunters. One of them has also become quite a proficient fossil diver. He’s always emailing me with news of his latest finds. Well this time, he sent me an actual find.

North Carolina and Chesapeake Bay waters are known to be rich in fossilized remains of creatures from the Miocene and Pliocene eras, around 23 to 3.6 million years ago. My buddy recently sent me a pretty decent-sized shark tooth he found.

He didn’t find just one; he actually found four, which is probably why he sent me one. But it was not from just any shark. It was one from a shark species now long extinct called the megalodon shark, better known as the Meg.

Megalodon tooth with two great white shark teeth and with a centimeter ruler to see the size. Photo by Brocken Inaglory, Creative Commons Attribution-Share Alike 3.0 Unported

Looking up info on the megalodon was fascinating. They have been identified as the largest shark ever to have existed, with 10-foot-wide jaws! Scientists are not all that sure when it first showed up, but they think it was gone by the end of the Pliocene, which ended about 2.6 million years ago.

That has not stopped Hollywood from cranking out a few movies, one even called “The Meg,” about scientists bringing them back to life or growing them in a petri dish like Jurassic Park.

Largest shark EVER! Like Brody (Roy Scheider) says to Quint (Robert Shaw) in the movie “Jaws,” “You’re going to need a bigger boat!”

Over 170 years ago, Swiss naturalist Louis Agassiz gave the Meg its initial scientific name. His thinking was that its teeth were morphologically similar to great white sharks (Carcharodon carcharias) so assigned megalodon to the same genus, Carcharodon. Thus it was dubbed Carcharodon megalodon, although more informally called the giant white shark or megatooth shark.

But scientists have since revised their thinking and now call it Otodus megalodon, which translates literally as “big tooth.” How original! In fact, scientists are kind of at odds with each other regarding most things known about the Meg.

Some think it may have been a species of mackerel shark. Others think it resembles a bigger edition of the great white, while some think more likely a whale shark, while still others think a basking shark — and yet still more think it may have been more like the sand tiger shark.

The author showing both sides of a megalodon tooth. Photo by Charles H. Lagerbom

Why can they not agree on anything? Well, mostly because prehistoric sharks (like those of today) were mostly made up of cartilage, which does not survive well as a fossil. As a result, only teeth, parts of its vertebrae, and some coprolites from it have been found to survive in the record. Most common are its teeth. Lots and lots of them.

Basing what you are like, how big you are and your entire shape on only your teeth and a few vertebrae and some fossilized crap can get dicey. They do know that the tooth generally met the jaw at a steep angle, similar to the great white. The bases of Meg teeth are pretty rough and rugged, which leads some to think that that added to its mechanical strength or ability to easily crunch on big bones.

Studies suggest these teeth and large jaws were built for snatching prey and crunching bones, exerting a bite force of up to 182,200 newtons. A newton is a unit of force: The force of 1 newton gives a mass of 1 kilogram an acceleration of 1 meter per second per second. The Meg bite therefore may have resulted in over 41,000 pounds of force. That’s a bone cruncher for sure!

It appears the Meg was an opportunity feeder, but mostly feasted on larger prey, such as dolphins, small whales, cetotheres (baleen whales), squalodontids (shark toothed dolphins), sperm whales, bowhead whales, and rorquals. Fossil evidence indicates they also consumed seals, sirenians (sea cows and manatees), sea turtles, and smaller fish as well as other sharks.

The Meg’s hunting tactic appears to be unlike that of the great white, which attacks its target from the soft underside. It is suggested the Meg had the ability to just use its strong jaws to snatch the meal in mid-water and crush its chest cavity, putting it almost immediately out of action. Wow!

It appears they specifically targeted the heart and lungs and with their thick teeth adapted for biting through tough bone, quickly dispatched their prey. This was indicated by bite marks inflicted on the rib cage and other bony areas on fossilized whale remains. Yikes!

And it may have used different attack patterns for different prey, depending on their size. Fossil remains of some sea cows show compression fractures, indicating having been smashed into with great force from below, before they were killed and eaten. Imagine getting rammed by one of these things!

Fossil of whale vertebra that was bitten in half by a megalodon. Large gouge marks visible on the vertebra confirm such an interaction. Photo by Jayson Kowinsky, fossilguy.com

So just how big was the Meg? Scientists cannot even agree on that; it depends on which method you use. Today’s great white shark generally measures around 20 feet in length. Conservative estimates put the Meg in the 47- to 67-foot range; some suggest over 80 feet. Regardless, that is three to four times larger than a great white shark! A truck with a semi-tractor trailer is 65 feet long! And this one had ramming abilities and bone-crushing jaws!

Scientists estimate the largest of the megalodon sharks may have weighed over a hundred tons! That is similar to a blue whale, a Boeing 757-200 airplane, a locomotive engine or the Space Shuttle! And it was fast! A 2015 study estimated a Meg could attain speeds of 11 mph, consistent with other aquatic creatures of its size, such as the fin whale.

The Meg is considered to have had a cosmopolitan distribution, which means its range extended all across the world in appropriate habitats. Since today’s sharks prefer warmer waters, scientists think the range for the Meg extended up the U.S. East Coast, maybe to New England waters, maybe even up to 55° North. If I find a Meg tooth in Maine waters, I’ll let you know!

The preference for warmer waters is considered one reason for its eventual extinction. Oceanic cooling occurred with the onset of the ice ages, limiting its distribution. Lowering sea levels also affected its area of operations and contributed to its decline. Since its range did not extend into colder waters, the Meg may not have been able to keep much of its metabolic heat. Its range would have been constrained by increasingly shrinking warmer waters and declining temperatures during the Pliocene.

Today, the whale shark is the largest living fish; some have been found to reach almost 60 feet. It is possible the Meg exceeded that size range — especially if its food source was prolific — and during the warm Miocene, it apparently was. It was a true apex predator. The Megalodon is considered to be the largest macro-predatory shark that ever lived.

My buddy said that fossil hunting off the Carolina coast and in the Chesapeake is best during the winter months, especially after storms or strong winds have churned up the bottom. Many fossils he has found have been in 5 feet of water or less. Megalodon teeth are actually the state fossil of North Carolina. So now I might have to go down and visit and try to find a few myself!

Charles Lagerbom teaches AP U.S. History at Belfast Area High School and lives in Northport. He is author of “Whaling in Maine” and “Maine to Cape Horn,” available through Historypress.com.