Jessica Keenehan swims in the lagoon near her home in Loveladies every evening, and had never been stung by an Atlantic bay nettle until recently. The irritation and subsequent itchiness weren’t pleasant, but Keenahan is well aware she’s in the territory of these jellyfish – and an occasional sting is often part of spending time in our coastal New Jersey waters.

“We see bay nettles all the time in the bay, and we’ve seen a lot this summer,” said Keenahan, a year-round resident who owns Unique 2…