Visitors to Muckross Bay in Fermanagh have been warned of a harmful blue-green algae near the popular visitor attraction.
The advice comes after the emergence of an acquatic plant at Muckross Bay in Kesh.
Fermanagh and Omagh District Council have now erected signage to spell out the danger of the blue green algae.
"We advise that adults, children and animals should avoid contact with the algae and the water close to it due to its harmful effects," a statement from the Council read.
"Swallowing the water can cause stomach upsets or severe illness to people and death to animals. Contact with the water or the blue green algae can also cause rashes and skin problems," it added.
Fermanagh and Omagh District Council say they routinely monitor the area's rivers and lakes - saying they take the utmost care in monitoring their water quality.
They also say steps will be taken to "closely monitor" the situation at Muckross Bay.
"The Council will continue to closely monitor the blue green algae at Muckross Bay with warning signage remaining in place until the algae has cleared."
If you have any concerns regarding the blue green algae Council are urging anyone with any issues to contact their Environmental Health Service department on 0300 303 1777.