WATCH: Dangerous Jellyfish, With Severe Sting, At Jersey Shore

A Point Pleasant man said on the Barnegat Bay Island Facebook that he “saw this thing swimming around” in the Mansasquan River.

But he knew what it was - probably. And experts say it was dangerous, an exotic jellyfish with a severe sting.

It was a probably jellyfish, and it was next to Gull Island, Point Pleasant Beach. The individual said it was six-to-eight inches long, “translucent grey blue with the orange tentacles,” he said.

“It swam around that immediate area and kept going back to the same spot. It also surfaced, over and over as if to breath as it broke the surface. It actually seemed somewhat intelligent.”

The reature is believed to be a box jellyfish with a severe sting, said Paul Bologna, director of the Marine Biology and Coastal Sciences Program at Montclair State University in Montclair, according to APP.

“Sea nettles are nothing compared to these guys,” he said, referring to the stinging jellyfish that have plagued Barnegat Bay in recent years. Box jellies can deliver “a pretty severe sting. They can be very painful,” he said, according to the APP.