Authorities in Ghent (Belgium's third-largest city, known for its historic canal network) have detected blue-green algae, also known as cyanobacteria, at multiple locations across the city's inland waterways. Swimming is already prohibited in these waterways, and officials are now strongly advising against water sports such as kayaking, warning that anyone who proceeds does so at their own risk. The bacteria can release toxic substances that, if ingested, may cause symptoms ranging from headaches and skin irritation to nausea, fever, and diarrhoea, with prolonged exposure potentially damaging the nervous system and posing risks to animals as well.