VISITORS to Frensham Great Pond and Common are being warned not to enter the water because of the potential presence of blue-green algae.
Waverley Borough Council rangers spotted the appearance of the algae on Monday (July 13) and notified the Environment Agency, which is set to attend the site to carry out checks.
The council has now taken the precautionary measure of advising people not to swim, paddle or enter the water.
Signs instructing visitors to avoid contact with the algae and not to enter the water will be put up at the site.
Blue-green algae are a natural component of a freshwater ecosystem, but their presence is potentially harmful to humans, animals, birds and fish.
Periods of warm weather followed by heavy rain and then further warm, still conditions cause blue-green algae to appear suddenly.
Although not all species of the algae are harmful, Waverley Borough Council has recommended people avoid the water, as contact with the algae can cause dermatitis, eye irritation, rashes, blistering, abdominal pain, diarrhoea and nausea through contact with skin, eyes or if swallowed.
Anyone believed to have been affected by blue-green algae should seek medical advice.
The council has assured residents it is monitoring the situation closely and will keep the public notified through the Waverley website.