The NSW government has revealed the cleanest and dirtiest beaches to swim at in Sydney, as the Harbour City prepares for a hot summer.

Temperature records are already being broken, leading Sydney's residents to flock to the 97 beaches around the city to beat the heat.

The latest BeachWatch State of the Beaches report reveals the Northern Beaches have the cleanest water in Sydney, with all but one of the beaches in the top 10 being in the area.

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Several factors are used to measure the water quality.

One of these is measuring the level of a bacteria called enterococci.

It is an indicator of germs present in water that can cause gastrointestinal illnesses, as well as rashes.

Swimming in beaches and waterways is cons

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