Minutes after his carrier was opened, Professor X hopped happily into the Atlantic Ocean for the second time in six months.

Biologists from the Riverhead Foundation for Marine Research and Preservation released the male gray seal into the waters off Ponquogue Beach in Hampton Bays just after 1 p.m. Thursday, completing a journey that took the seal from Long Island’s South Shore to a canal in upstate Waterford and back.

The foundation picked up the seal from Robert Moses State Park in April, treated his injuries and then released him in the Atlantic on July 15. About two weeks later, researchers began hearing reports of a seal in the Champlain Canal in upstate Waterford.

“It’s an interesting occurrence that we see a seal up the Hudson that far,” said Robert A. DiGiovanni Jr., the foundation’s executive director and senior biologist. “The seal that was up there was doing well, feeding, doing what it should be doing.”

New York State Canal Corporation workers began to refer to the seal by a number of names — Sal, Sammy, Wrong Way Charlie and Courage, according to a post on the corporation’s Facebook page Wednesday afternoon.

“Over the last several months our staff and neighbors kept an eye on him while he freely swam and ate in the navigation pool between Locks C-1 and C-2,” the post read.

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But the Riverhead Foundation said the seal was unintentionally contained when state officials closed off and began to drain Lock 1 for maintenance. A group of biologists went to retrieve the juvenile male on Friday.

The seal, who had apparently traveled up the Hudson River after his July release, was taken back to the foundation’s Riverhead facility and evaluated. DiGiovanni said the seal was determined to be healthy, and was, surprisingly, a return guest to the research facility. A flipper ID revealed him to be Professor X.

The foundation’s biologists don’t often see the same animals again, he said.

“It’s a pretty rare occurrence; it’s probably only happened a handful of times in 20 years,” he said. “This happened to be a situation where everything aligned.”

Just before Professor X was released again, biologists put a satellite tag on his body. DiGiovanni said they do this as often as possible with the animals they rehabilitate. The tag will allow them to find out where Professor X travels next, even if it is back to the Hudson River.

“This will enable us to track him and see where he goes and what he does,” he said.

DiGiovanni said the rescue was a testament to vigilant people who called the foundation’s 24 hour stranding hotline at 631-369-9829.

“This wouldn’t be possible at all without the people calling into our hotline number,” he said. “We were lucky and fortunate enough to have the help of concerned citizens.”