A video showing what appears to be an unidentified creature in the Han River has gone viral, according to local media reports Wednesday.

The video titled “A Real Monster Emerges at the Han River in Seoul” was posted July 11 by fishing-themed YouTube channel Jungdam Story. It shows the YouTuber fishing at night near a parking lot by the National Assembly in Yeouido, when he spotted something large and moving in the water.

At first, he thought it was a big fish. Upon closer observation, he appeared alarmed by what he described as a black, thick and long creature approaching him.

“What is that? I’m scared. It’s moving toward me,” he said in the video, before abandoning his fishing spot.

He said the creature remained in the same area for about 20 minutes, moving consistently. He estimated it to be 6 to 10 meters long and thicker than a human body.

“It looked like there were two of them,” he added. “I’ve been fishing for decades, but I’ve never seen anything like this before.”

The video has sparked thousands of comments online. Some speculated that the creature could be a group of otters, an alligator or even a python.

In 2022, a similar popular video showed an unidentified object of comparable size in the Han River, which was later identified as a buoy.