Swimmers have had to worry about the increasing presence of stinging sea nettle jellyfish in the Barnegat Bay, but a rare and more dangerous species of box jellyfish with venomous tentacles could reappear in the ocean along the Jersey coast this year.

Pacific Sea nettle jellyfish. (Ethan Miller, Getty Images Entertainment)

Through DNA testing, Montclair State University researchers last week confirmed, it was a box jellyfish that washed up on a Bay Head beach last fall, according to the Asbury Park Press.

"For the unfortunate encounter with one, I'd be very concerned because it's known to have a very potent venom and it's one of the nastier jellyfish you can bump into," said Dr. Stan Hales, executive director of the Barnegat Bay Partnership in Toms River.

Box jellyfish stings leave a burning pain, swelling, blisters and can cause scarring. According to Hales, for the most part, a box jellyfish is an oceanic species and people aren't really likely to ever encounter one. He doesn't expect them to become common in the bay, unlike the large blooms and dense concentration of sea nettles seen over the past several years. "It's definitely something to be concerned about and to keep your eyes out for them, but I think it's a really unusual occurrence, a rare occurrence. That's not to say, our world is changing and conditions could be a little different and maybe we see them a little more abundant or more frequent," Hales said, adding that there is not a lot of evidence to suggest that.

Last year, six rare sightings were reported by Shore residents on beaches in Ocean County. One was spotted in the Manasquan River. Box jellyfish live in warm coastal waters worldwide and could have been carried by the Gulf Stream to the Jersey Shore, according to experts. Hales said jellyfish have a complicated history. "They go through what's called an alternation of generations. They have a polyp stage that's attached to a hard substrate, such as the underside of a floating dock, or rocks, or oyster shell, or something on the bottom, and that's how they actually spend the colder months," Hales said. "The jellyfish that we see floating around in the water is a sexual being; it's male or female, but it's a seasonal thing. It's only here basically for a restricted period of time." Although he's not terribly concerned about box jellyfish becoming more abundant at the Jersey Shore, Hales says, "That's not to say it can't happen."

Jack Gaynor, an associate professor of biology at Montclair State University, told the Asbury Park Press he's convinced the box jellyfish found in Bay Head is a Tamoya haplonema. He said further testing was being done to learn more about the species. The box jellyfish also is known as the sea wasp or the marine stinger and is one of the most dangerous of all species of jellyfish in the world, according to bioexpedition.com. It also is nicknamed "Sucker Punch Jellyfish" because victims won't see them coming until it's too late. The website suggests getting someone who has been stung out of the water quickly.