Fin of shark appears off South Beach on July 6. — John Kisalus

It was not so much a matter of life imitating art as of life contradicting art.

More than 30 years ago, when they were filming the movie Jaws on Martha’s Vineyard, a young Jonathan Searle played the part of a kid who scared people out of the water by using a fake fin to pretend to be a great white shark.

But just a few days ago the same Jonathan Searle played a different role. Not the guy who carries out the shark hoax, but the police officer who busts the guy who carried out the shark hoax.

It happened like this, according to officer Searle’s police report.

Around 10.40 a.m. Friday, officer Searle was off duty and on State Beach when he saw a man approach a woman who was throwing a tennis ball into the ocean for her dog to fetch.

The man told her to keep the dog on shore because there were two huge great white sharks swimming in the area. The man pointed out a Coast Guard cutter anchored offshore and said the sharks were the reason it was there.

The man told the woman he was a fisherman, and had earlier spotted the sharks near the shore, inside the swimming buoys, approximately 150 feet from the beach.

Then the hoaxer approached another group of people, four adults with five children, and told them to get their kids out of the water because of the sharks.

Additionally, said the report — which reads more like a script, really — the man said he had been in a 44-foot boat when he saw the sharks, which “about as long as the boat and weighed between 3,000 and 4,000 pounds.”

The man moved on down the beach, talking to other groups of people, who promptly called their children back to the beach.

Officer Searle had to get to work to begin his shift with the Edgartown police. So he left the beach, and when he got to work, found that State Beach had been closed.

But he knew the identity of the man who had made it happen: one Michael A, Lopenzo, 60, of 17 Court street, Boston. When subsequently questioned, Mr. Lopenzo said he had told at least 30 people, including a female life guard, about the sharks. He said he had six kids of his own and thought it the right thing to do.

Asked about the boat he had allegedly been on, Mr. Lopenzo said it was the Alicia Li, 38-foot lobster boat, out of Oak Bluffs. He said he had been out catching lobsters and crabs when he saw the sharks.

He said the owner of the boat, one John Kennedy, had also seen them.

Checks revealed no such boat or owner, and so Mr. Lopenzo was charged with disorderly conduct.

“Based on my investigation,” officer Searle’s report says, with masterful understatement, “there is no credibility to be given to Michael Lopenzo’s shark story.”

But, as the blurb said for the Jaws sequel, just when you thought it was safe to go back in the water, it might not be.

For while the State Beach shark sighting was a hoax, there is evidence there is something out there.

Life guards at South Beach saw a fin the same day and closed that beach. Spotters in a plane saw something. And it was not the first time; about a month ago fishermen saw what they thought was a great white near the beach at Menemsha, and there is no reason to believe they were making it up.

And just yesterday, more disturbing news washed up on South Beach — the carcass of a seal, several days old, and possibly the victim of a shark.

We will not know that for sure until later today, when Greg Skomal, a shark specialist for the State Division of Marine Fisheries, returns to Martha’s Vineyard to examine the decomposing body of the seal.

But there are those who believe the population explosion among gray and harbor seals in the Cape and Islands region over recent years may be attracting big sharks.

We found Dr. Skomal yesterday, (after contacting his assistant John Chisholm, whose cell phone features, as its hold music, the theme from Jaws), and he conveyed some disturbing developments.

“It’s no secret the gray and harbor seal population has been increasing over the past couple of decades,” Dr. Skomal said.

“We do know that white sharks in the Atlantic tend to feed more on dead whale carcasses than on seals, but that is something that may be changing as seals become relatively more abundant.

“There are now a number of sizeable populations, on that new sandbar which has appeared off Wasque Point, on Muskeget Island, on Monomoy island.”

And something big is eating them.

“Last year we from the Monomoy area, [off the southern end of Cape Cod] there were some dead seals that clearly, in our view, had been attacked by large sharks,” he said.

As for the Menemsha sightings, he said: “We talked to the fishermen involved. There’s no reason to cast doubt what they say they saw, although we didn’t see it.”

Dr. Skomal has no doubt there were great whites out there. He’s seen them before. The problem is, no one really knows how many, or if their numbers are increasing, or if their dietary habits are changing and bringing them in closer to the Vineyard.

“In relation to white sharks we don’t have very good population data,” he said. “It’s such a rare event species. If we’re talking one or two individuals or 10 or 15, it’s hard to tell.”

But, he noted, no one had ever been taken by one on the Island. None had ever been caught during any of the various shark fishing tournaments here or elsewhere in the region. Indeed, there were only three recorded shark attacks, ever, in Massachusetts waters.

But he was enthusiastic about looking for them.

“If we can pinpoint the location of one of these critters, we’re going to try to go out and tag it,” he said.

Meanwhile, the idea of one or more great whites swimming around the island where Jaws was made has fueled wide interest, and the odd gag.

A fin now protrudes from the water hazard on the 10th hole at the Edgartown Gold club. A similar thing has been done at the Chappaquiddick Beach Club.

Edgartown police chief Paul Condlin reported having been inundated with phone calls from media ­— the Boston Globe, CNN, the Associated Press and others — and he had the sense they wanted an attack.

The Gazette yesterday fielded a call from a reporter from the BBC in Scotland, who wanted an interview, and e-mailed a list of questions including “When was the last shark attack on Martha’s Vineyard?”