South Korean authorities managed to lure the shark out of the artificial canal in Busan on Wednesday. It had spent the previous few weeks there.
However, less than a day later, officials discovered that the three-meter-long dusky shark was back.
"The shark is now between the outer and inner nets set up 30-40 meters into the channel," an official told AFP.
The shark has attracted great interest, and more than 1.6 million people have come to the channel to see it.