Authorities in the south-eastern South Korean city of Busan made a third attempt on Wednesday to send a trapped shark back to the open sea.
City and Coast Guard officials scanned the water from the shore and from a makeshift bridge, while divers went in.
The team used a net secured to a pontoon to guide the animal towards open water. At several points, it was seen swimming close to the shore.
Onlookers gathered along the banks to watch. The shark first appeared in the waterway on 18 September, and more than a million visitors have come to see it since.
By late Wednesday afternoon, it was still unclear whether the operation had worked.