The Marine Mammal Stranding Center (MMSC) said the pup was still covered in his white birthing coat after being discovered at the 48th Street beach.
He weighed just 36 pounds, or about 60 to 70 percent underweight for his age.
He's believed to have migrated 400 miles from "pupping grounds" in Maine. It's the fourth seal to wash up on the Jersey Shore this year,
"This little pup likely did not learn how to eat on his own after being weaned from his mother," the MMSC said on its Facebook page.
The seal wasn't successfully feeding himself, so he dropped back down to close to birth weight by the time he completed his marathon swim
Once the pup arrived at the center, he was moved into the ICU and given supportive care with fluids and assistance eating fish.
He is now sporting his black juvenile coat. "This little pup will stay with us until he has recovered and gained weight before being released back into the wild," the center said.
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