• Avoid swimming after heavy rainfall (more than 10 mm) – typically for one day in coastal waters, or up to three days in rivers or estuaries.
  • Look around and assess the water quality before you go in. Avoid water that is discoloured, murky or smells unpleasant.
  • Avoid swimming in warm, slow moving or stagnant water.
  • Look for any drains actively flowing into the water. If you see one, find somewhere else to swim.
  • If you see sick or dead marine life, avoid the water.
  • Check for any advisory signs and follow their advice.
  • If you have an open wound or infection, avoid swimming.
  • Stay out of the water if you have diarrhoea or are vomiting.

Water quality of natural water sources, such as beaches and rivers, can vary greatly. Keeping a lookout for poor water quality (such as water that is discoloured, murky or smells unpleasant) will help you decide when it is safe to enter the water. By paying attention to a few noticeable signs, you can keep yourself safe.

People with weaker immune systems (including children and the elderly) face a greater risk of developing swimming-related illnesses, and should take particular care. 
When at the beach, use nearby toilet facilities and take children on regular toilet breaks. Stay out of the water if you have diarrhoea or are vomiting. If you have an open wound or infection, avoid swimming.

Warm, slow moving or stagnant water should be avoided. Do not swim if you see sick or dead marine life in or near the water. Dispose of all waste hygienically if you are boating.

If you are uncertain and notice any signs of poor water quality, do not swim.

Microbiological pollution

Microbiological pollution is made up of harmful microorganisms called pathogens, such as bacteria and viruses. These microorganisms contaminate water and sand, and reach the water via:

  • stormwater runoff
  • boating pollutants
  • sewage (including malfunctioning septic tanks, spills and animal droppings).

If you swim in or swallow polluted water you may become ill, most commonly with gastroenteritis (gastro). Gastro is a short-term illness. Symptoms include:

  • eye, ear, skin and upper respiratory infection
  • vomiting
  • diarrhoea
  • stomach pain
  • nausea
  • headache
  • fever.


Stormwater runoff is rain that does not soak into the ground, but runs across the surface into the manmade drainage system. From there it flows untreated into natural water sources, including bays, rivers and lakes. Stormwater runoff can carry pollutants such as:

  • litter – cigarette butts, cans, food wrappers, plastic bags and other rubbish
  • natural pollutants – leaves, sticks and animal waste
  • chemical pollutants – fertilisers, detergents, fuel and oil.

After heavy rain (more than 10 mm), natural swimming spots can be more polluted from stormwater runoff. In general, it’s best to avoid swimming in coastal waters for one day after heavy rain, and in rivers and estuaries for three days after heavy rain. Visit the Environment Protection Authority (EPA) website for advice.

To be safe, pay attention to advisory signage about rain impacts, and avoid swimming near stormwater drains.

Sewage spills

The Melbourne sewerage system is designed for flows of up to 25 mm per hour. Any more than that is considered an extreme storm event. When handling this kind of overflow, sewage may be discharged at designated overflow points. These overflow points are located at less sensitive spots in the sewerage system.

To be safe, avoid swimming anywhere with a storm water drain. If water is actively flowing from a nearby drain, find somewhere else to swim.

Water quality monitoring

The EPA monitors 16 fixed sites across Port Phillip Bay, Western Port Bay and the Gippsland Lakes. It looks at water trends over time, measuring changes in nutrient levels, algae composition, oxygen conditions, toxicants and water clarity.

The EPA also runs Yarra Watch, which provides water quality forecasts for four sites along the Yarra River from December to April each year.

For more detailed information, you can find water quality data on Victoria’s rivers, streams, lakes, estuaries, bays and water storages through the Department of Environment, Land Water and Planning.

Beach Report

Beach Report lets you know what the water quality is like at 36 beaches around Port Phillip Bay. Forecasts are issued twice a day during the warmer months. You can also get these forecasts via Twitter (@EPA_Victoria) or by checking the signs at your local beach.

The three types of forecast are:

  • good – fit for swimming
  • fair – usually issued after rainfall, may indicate that the beach is near a stormwater outlet
  • poor – avoid all contact with the water.

Other alerts may be issued all year round. These alerts may include:

  • pollution incidents
  • fish deaths
  • algal blooms (blue-green algae).

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Last updated: September 2017

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