MONMOUTH BEACH, N.J. (CBSNewYork) — As the beach weather returns to the Jersey shore, so have some unwanted visitors.

A dangerous species discovered down the shore last summer is back.

As CBS2’s Meg Baker reported, the clinging jellyfish is back. It’s no bigger than a dime, but its sting can be deadly.

“I do swim, so I’ll keep a lookout,” Mary Pennella said.

Nearly invisible during the day, the invertebrates glow at night when it is most active.

Professor Paul Bologna was out on the Shrewsbury River and found over 150 clinging jellyfish, a sign the extremely potent jellies may be here to stay.

“Invasive species from the specific ocean all of a sudden they magically showed up last year, so trying to figure out where they came from,” he said. 

Jellyfish usually die off by September, but Bologna said their team discovered small polyps that cling to seagrass and survive harsh winters.

Scientists said there is no need to worry about going in the ocean — the little terrors prefer the calm waters of back bay areas.

“That may put you in conflict if you are kayaking, paddle boarding, and you fall into the shallow areas where they might be located. So we recommend wearing wet suit skin to keep yourself protected,” Bologna said.

If stung, call 911 immediately. The toxic sting attacks your nervous system and immobilizes muscles giving a Charlie horse sensation.

“When you get stung by them, they are really potent. And they basically cause your muscles to seize up,” Bologna told WCBS 880’s Peter Haskell.

So far this season the dangerous jellies have only been found in the Shrewsbury River.

The biologists will extract DNA to research an anti-venom protection. Professor Bologna will host a jellyfish presentation at Island Beach State park on Saturday at 2 p.m.

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