Holidaymakers bathing on a popular beach have reportedly been stung by the country's most toxic fish.
They received "excruciating" stings from the poisonous weever fish lurking in wet sand.
The normally shy creatures, which are only 10cm long, hide in the sand, but deliver a sting described as "worse than a wasp sting".
Incidents have been recorded at Criccieth beach in North Wales. Similar reports were noted at other beach locations in the area, including Harlech and Tywyn.
Typically docile, the sand-coloured weever fish are camouflaged, meaning paddlers often unwittingly stand on them.
At first, many victims believe they have simply scratched themselves on a sharp stone or shell, but significant pain follows two or three minutes later.
The venom comes from long spines along its back that carry a powerful neurotoxin that inflicts extreme pain within minutes of contact. These needle sharp barbs easily pierce through human skin - and has even been known to penetrate through a wellington boot.
The pain can last for several hours, with the flesh around the sting become red, swollen and inflamed - and can even cause localised paralysis.
Beachgoers are now being advised to wear appropriate footwear such as trainers or surf shoes and to avoid going barefoot when paddling in the water to avoid injury from the tiny creatures, NorthWalesLive reports.
In 2016 a 64-year old fisherman from Wrexham received a sting and was airlifted to hospital after suffering a severe reaction.
A spokesperson for Criccieth Lifeboat said: "Following multiple cases of people being stung by weever fish on Criccieth beach, we urge beachgoers to wear appropriate footwear whilst paddling."
The weever fish’s sting is painful but not normally serious. Affected areas should be bathed in warm water and if symptoms persist or the wound becomes inflamed, consult a doctor.
