Off the south coast of Massachusetts sits Chappaquiddick, a long, narrow strip of land that — depending on the tides — is either an island or a peninsula that's barely connected to Martha's Vineyard.

A long beach runs along the east side of the island, beckoning tourists and locals to its sandy shores and wildlife sanctuaries.

But under the beach chairs and picnic blankets lies a mystery 100 years in the making — an old shipwreck, buried in the sand.

For the most part, the ship's remains are invisible to the casual beach goer. But every now and again, a storm will uncover the pieces and reignite speculation about the origins of the doomed vessel, which have yet to be resolved.

According to the Martha's Vineyard Gazette, where we first learned about the wreck, the ship has been uncovered at least three times since Hurricane Sandy blew over the island in 2012.

Here's a photograph of the shipwreck's remains, taken in February 2016:

Arnold Carr/American Underwater Search and Survey

It may not look like much, but the wreck is a gem in the eyes of experts.

"It's in remarkably good shape," marine biologist and shipwreck diver Arnold Carr told Tech Insider. "It hasn't weathered that much nor have marine worms eaten it."

Marine worms, sometimes called ship worms, are a species of clam that eats wood, making it the bane of marine archaeologists working on saltwater sites.

Carr, a Martha's Vineyard native, said that rough winds sweeping over the island for at least the last two decades have periodically uncovered and recovered the wreck. "It'll disappear for a year or two then be exposed again," he said.

When the ship does appear, its timbers, planking, and iron bolts stick out from the sand. Carr said the wreck is between 60 and 70 feet long and 40 feet wide, and lies parallel to the water. Under the sand, he added, there might be more of the wreck, bringing the total length to 100 feet or more.

Arnold Carr/American Underwater Search and Survey

"It probably got blown ashore," he said, adding that violent storms near Chesapeake Bay make it a treacherous area to sail. Colloquially, the area is known as "the graveyard of the Atlantic."

Carr, whose diving outfit American Underwater Search and Survey discovered the wreck of the Portland 100 years after it was lost at sea, says that the enigmatic schooner probably dates to the mid-1800s, given the construction of the ship — the iron bolts in particularly — and historical data he's gathered from public archives.

"Within one mile of the site there's at least three ships that sank in the area," Carr said. "My best estimate would be 1850s or early '60s."

At first, Carr said, he thought the wreck might part be the Christina, which went down in a blizzard in 1866. Writing in the Martha's Vineyard Gazette, reporter Tom Dunlop described the wreck as "one of the most notorious disasters on island waters in the 19th century." All but one of the Christina's six crew died in the wreck, with the lone survivor losing his fingers and feet to frostbite.

Carr has since changed his mind, saying that the location doesn't quite match with where he'd expect the Christina to be.

Now he thinks it may be the Silver Bell, a schooner which sank in the 1850s — but records from the time are scant. One report from 1863 lists the ship only as "Schooner Silver Bell, Cape Poge. Total Loss."

It's tempting to connect the dots: Cape Poge is on the northwest side of Chappaquiddick Island, and no remains of the Silver Bell have ever been found.

But for archaeologists to identify the ship, a research team would need permission from the state and local governments to excavate.

For now, the ship remains hidden and preserved under the sand, capturing the imaginations of future generations of shipwreck hunters.