Mass. sharks and seals are the stars of a new National Geographic documentary

Sharks close off shore near Long Nook Beach in Truro.David L. Ryan/Globe Staff

Massachusetts seals and sharks were the stars of a new National Geographic documentary that may give local beachgoers cause for concern when swimming off the coast of Cape Cod.

The documentary, “Return of the White Shark,” which premiered on July 2, highlights the work of researchers such as Gregory Skomal, a senior fisheries scientist at Massachusetts Division of Marine Fisheries, and other shark specialists around Cape Cod’s National Seashore who share first-of-its-kind research that helps viewers learn about shark behavior.

“The documentary did a great job,” Skomal said. “It really highlighted the work we’re doing and the recurrence of white sharks on Cape Cod and their co-occurrence with humans and it touched specifically on the various research projects we’re running.”

As featured in the documentary, that research includes camera behavior tagging, in which Skomal and his team deploy tags onto sharks to try to answer the question of when and where white sharks are most likely to be feeding on seals, Skomal said. The researchers show how they use drones to monitor how close sharks come to the shorelines and interact with human presence.

“We’re very much interested in observing white sharks when they approach the shoreline to see how they behave, how they might interact with each other, how they might interact with their potential prey, seals, and how they act in the presence of humans,” Skomal said. “Because let’s face it, there is human overlap in some of these areas with white sharks.”

Although shark sightings are common in Massachusetts today with the resurgence of seals and their predators, this has not always been the case.

Up until almost the turn of the century, it was legal to recreationally fish seals and sharks in the United States, making their populations scarce along Massachusetts shorelines. But Skomal said that in 1972, seals were named a protected species under the Marine Mammal Protection Act. Then in 1997, sharks also became a protected species in the United States. Since then, the population of sharks has steadily increased every year.

“Twenty years ago, this was not something that people were thinking about,” Skolmal said. “But now seal populations are rebounding and they are recolonizing areas where they once were, which includes Cape Cod, and white sharks have taken notice because white sharks historically feed on seals.”

Many remember when a 14-foot shark got stuck in a pond near the Elizabeth Islands in 2004 — one of the first times locals had ever seen a living shark up close, in the wild. However, sightings like these are all too familiar today, and beachgoers should be cautious when swimming in the ocean.

“It’s a rare event, but sharks do bite people, and Cape Cod has had three bites since 2012,” Skomal said. “One in 2018 was fatal, so I think there’s legitimate concern on the part of beachgoers when it comes to sharks off Cape Cod.”

The Atlantic White Shark Conservancy, which contributes to the Division of Marine Fisheries’ white shark movement study, urges beachgoers to stay close to the shore, swim in groups, avoid areas where seals are present, and adhere to flag warnings and lifeguards’ instructions at beaches.

“What we ask people, particularly along the outer Cape, to do is watch out for the presence of sharks and the presence of seals, limit your activities to shallower areas, don’t swim alone, and know your own strengths and weaknesses in the ocean,” Skomal said.