Eighteen beaches have been rated 'good' in the Environmental Protection Department's latest water quality gradings.

Fourteen other beaches are 'fair' and one is 'poor'.

Siverstrand Beach's grading has been changed from 'poor' to 'fair' and Ma Wan Tung Wan Beach from 'very poor' to 'poor', while Big Wave Bay, Shek O, Clear Water Bay First, Cheung Chau Tung Wan, Kwun Yam and Silver Mine Bay Beaches have changed from 'good' to 'fair'.

The department said the changes are generally within the normal range of fluctuation of the bacteriological beach water quality.

Seven gazetted beaches - Anglers', Approach, Ting Kau, Casam, Gemini, Hoi Mei Wan and Lido - are closed to swimmers year round because of poor water quality. The public should not to swim at these beaches.

As beaches are likely to be more polluted than their grades suggest during and after heavy rain, bathers are reminded not to swim at beaches for up to three days after a storm or heavy rainfall.