Kingston, NY (AP) – A juvenile harbor seal has forgone life in the ocean, instead choosing a home nearly 100 miles up the Hudson River, behavior that wildlife officials called “unprecedented.”

The animal was likely abandoned as a pup by his mother in Maine, officials say. A Connecticut rescue center cared for him, then released him in Rhode Island in early 2019 with an electronic tracking tag.

By that August, he’d settled down on the Hudson near Saugerties Lighthouse, under the watchful eye of the lighthouse keeper, staying for 620 days.

“It is a story like none we have ever heard of … a marine mammal showing such extended affinity and fidelity to freshwater,” said Tom Lake of the state Department of Environmental Conservation’s Hudson River Almanac, The Daily Freeman reported Tuesday.

But the seal’s life on the river had one interruption.

Harbor Seal No. 246, as he’s known officially, disappeared last April, leaving wildlife officials stumped for months.

Turns out he needed rescuing again, catching an infection and a skin condition called “seal pox” after swimming down to Long Island’s Atlantic Beach.

Thankfully, Seal 246 was picked up by the New York Marine Rescue Center. Once he recovered, they released him last summer, likely expecting he’d head out to sea.

The critter had other plans.

He journeyed 210 miles, from Hampton Bays all the way back up the Hudson to his old stomping grounds near Saugerties. The lighthouse keeper noticed his return in August.