Water quality diving at Aussie beaches

Sydney beaches have recorded their worst water quality ratings in four years, but pollution at the popular Coogee Beach has fallen, new figures show.

Rose Bay Beach, Tambourine Bay at Lane Cove and Sutherland's Horderns Beach were among those to decline from good to poor ratings.

Foreshores Beach at Botany Bay has been rated Sydney's worst beach for the sixth year in a row, the only beach in NSW to be assessed as "very poor".

The State of the Beaches report, released on Monday, showed five in six Sydney beaches (84 per cent) were rated good or very good for water quality in 2016-17 - down from 86 per cent in 2015-16.

Prolonged rain and storm events were deemed to have contributed to Sydney's worst beach gradings in four years, but Coogee bounced back from a poor rating last year to just reach the threshold for a "good" rating.

Environment Minister Gabrielle Upton said it was a good example of the impact the report can have on government working to improve water quality.

"We had local council come together with the environment department and community groups and they've identified where the issues are and how they can best attack it," she told reporters at Bondi Beach on Monday.

"That has led to this better result (at Coogee) today."

Elsewhere in NSW, all seven of Newcastle's beaches were assessed good or higher.

Water quality is monitored once every six days while rating assessments are calculated off the back of each beach's past 100 samples.