The manatee has been spotted again, this time swimming up the Susquehanna River, where it empties into the upper Chesapeake Bay in Maryland.
It was also seen in the bay earlier this week.
The U.S. Geological Survey keeps a database of manatee photos.
Wildlife experts tell the big sea mammals apart by the markings on their tails.
Ilya hadn't been seen outside the Miami-area before arriving in Maryland.
Officials at the National Aquarium say Ilya looks fine, but he'll have to swim home before eastern waters get too cold in the fall.
