“Oysters settle on other oysters — historically, it was the dead shells that would serve as the base for the next generation,” said Mark Siddall, who described himself as “curator of wormy, slimy stuff” at the American Museum of Natural History. “That’s absolutely the story of New York, where new generations and new people build upon the remains of what was left behind.”

So Big is a metaphor for New York City itself — which, as the author Mark Kurlansky explained in his 2006 book, “The Big Oyster,” had another nickname before it was the Big Apple. By some accounts, in the 17th century, New York Harbor held half of the world’s oysters. The city was filled with oyster stands before there were hot-dog stands or food trucks. A 12-course dinner in 1842 for Charles Dickens — who characterized old Ebenezer Scrooge as being as “secret, and self-contained, and solitary as an oyster” — began with oysters, glorious oysters.

Big is a New Yorker, which means that Big is a survivor. Big survived being pried loose by a diver with the construction crew repairing Pier 40. Big’s people say dislodging an oyster is difficult; oysters attach themselves to objects underwater with cementlike inviolability. What happened to Big must have been traumatic, but was also its salvation. The construction workers “knew if they let it fall to the mud on the bottom, it wouldn’t survive,” said Toland Kister of the River Project.

The workers also knew Big wouldn’t survive the rest of the project, which will involve, in effect, power-washing the pilings and encasing them in cement, Mr. Kister said.

“It’s not as if people are diving down there to look for oysters all the time,” Mr. Kister said. “These were construction workers with a job to do, and it’s not research.”

Big’s people consider Big special, but they hope Big is not too special. “This oyster could be unique,” Mr. Kister said. “It could be the only oyster that was down there like this, but it would also be really, really cool if it wasn’t the unique thing down under there.”

Dr. Siddall said Big brought to mind oysters the size of dinner plates that were harvested from the Gowanus Creek in Brooklyn from the 1600s to the time of the Revolutionary War. “There was some dredging that was permitted in the late 1700s,” he said, “and after the dredging, the oysters were still abundant, but they were smaller.”