Microbiological contamination, e.g. untreated or poorly treated sewage, can cause a number of diseases. The most common are gastrointestinal illnesses such as diarrhoea, upper respiratory tract, eye, ear, nose or throat infections, and skin ailments. Chemical pollutants may also pose health risks but exposure to disease-causing microorganisms from untreated or poorly treated sewage is a greater risk. Swallowing contaminated water is the primary source of exposure to disease-causing microorganisms. They may also enter the body through the ears, eyes, nose or through broken skin.
Physical hazards are also possible when swimming in polluted water.
If water is not clear due to contamination or weed growth, objects like rocks and broken glass are much less visible and more likely to cause injury. There are many ways individuals can help to keep recreational water safe. Avoid going in the water if you have an open wound or an infection. Don't use soap in recreational water. Soap nourishes algae and bacteria, helping them to grow.