The small, sandy-coloured fish, about 15cm long, spend most of their lives buried just beneath the surface, leaving only their spiny dorsal fins exposed. Their sting, delivered when stepped on, can cause severe pain, swelling and redness.

Two councils, Mid and East Antrim and Causeway Coast and Glens, have issued warnings following more reports of incidents. The fish are found throughout UK waters but appear more frequently in summer, with warmer weather contributing to rise in encounters.

RNLI lifeguard Maria Dillion, who patrols Portrush West Strand, said she has seen a noticeable increase this year. “With more people coming to the beach we’ve had more stings, and a lot of people don’t know what they are,” she said. Victims often describe the initial pain as “like stepping on a sharp shell,” followed by throbbing that only eases when the sting is submerged into hot water.

Surfers and swimmers along the coast have had painful encounters. Last year, surfer Eve Curry was stung during a lesson: “It felt like a line of pain through the bottom of my foot… I didn’t know what it was until the instructor told me.” Others, like Norma Rae, narrowly avoided stepping directly on the fish.

Surf instructor Andrzej Krystowski said stings have been “particularly bad this year,” with sightings reported across the north coast. “They’re everywhere and you can’t see them,” he said.

Officials advise wearing wetsuit boots or water shoes in shallow waters. While the number of cases formally reported to councils remains low, authorities say the painful sting and risk of adverse reactions justify warning the public to stay alert.