BLUE green algae has been confirmed within Brooklands Lake at Brooklands Park.
The Environment Agency has confirmed that the algae has formed due to silt forming on the lake bed and the increase in water temperature.
Visitors are advised to avoid contact with the water and to keep pets away from it until further notice.
Contact with the water could result in skin rashes, eye irritation, vomiting, diarrhoea and fever and pains in muscles and joints can occur if any users of the water have swallowed or swam through algal scum.
Visitors are advised to seek medical help if they experience any of the above symptoms.
Worthing Borough Council staff are checking the lake daily. Brooklands Pleasure Park is open for business as usual.