CHARLESTOWN, R.I. (WPRI) ─ State health and environmental officials are warning swimmers that “a high abundance” of Atlantic sea nettle jellyfish have been spotted in two Charlestown ponds.

The R.I. Department of Environmental Management’s Division of Marine Fisheries has reported high numbers of the jellyfish in Ninigret and Green Hill ponds.

Sea nettles, according to the DEM, are commonly found during the summer months in salt ponds throughout South County.

Katie Rodrigue, a marine biologist with the DEM’s Division of Marine Fisheries, said the sea nettle jellyfish population “has been exploding over the last month or so” in both ponds.

Last week, Rodrigue said, they spotted thousands of jellyfish in the western section of Ninigret Pond, near East Beach.

The reason for the increase in the jellyfish population is unclear at this time, but the R.I. Department of Health is advising those who plan to swim in those ponds to bring a bottle of vinegar and sting spray with them just in case.

While reactions to sea nettle jellyfish stings vary, most people experience moderate discomfort. Symptoms include a burning or stinging sensation, swelling, itching, redness and blistering.

If stung, the Health Department recommends removing the visible tentacles with a gloved hand or plastic bag and rinsing the affected area with vinegar or a commercially available sting spray.

To lessen the symptoms, the Health Department suggested soaking the affected area in hot water, applying an ice pack or using hydrocortisone cream.

If the symptoms worsen, the Health Department advises seeking medical attention.