UPDATE: Melburnians may be able to swim at the city’s beaches today after the bay was contaminated by faecal matter yesterday.

Environment Protection Authority on Monday afternoon gave a poor water quality rating to 21 beaches in Port Phillip Bay, including the popular St Kilda, Elwood and Frankston.

SECRET MELBOURNE BEACHES YOU'VE PROBABLY NEVER HEARD OF

Other beaches given a poor rating include: Seaford, Carrum, Aspendale, Mordialloc, Mentone, Beaumaris, Black Rock, Half Moon Bay, Sandringham, Hampton, Brighton, South Melbourne, Port Melbourne, Sandridge, Williamstown, Altona and Werribee.

media_camera Dirty beachwater at Albert Park last Friday after torrential rain and storms. Picture: Stuart MIliigan.

Environment Protection Authority Victoria said on Tuesday that conditions had improved at the city’s beaches overnight after a torrential downpour last Thursday sent large amounts of faecal pollution washing into Port Phillip Bay.

All 36 bay beaches are suitable for swimming and are rated as either good or fair, EPA spokesman Dr Anthony Boxshall told AAP, but people should still avoid swimming in discoloured water or near stormwater drains.

Dr Boxshall previously said: “We have indicators we look for (in water tests), which is an indicator of faecal contamination, which is a really nice way of saying poo,” he said.

“It’s bird poo, it’s horse poo, it’s cow poo and it’s people poo.

“It is everything that washes in from the streets, and everything that comes out through the storm water system.”

media_camera Andrew Lister with his sons Owen and Billy walk along the filthy beach at Albert Park last Friday. Picture: Stuart Milligan.

Beaches on the Mornington Peninsula and Geelong were deemed safe to swim.

Dr Boxshall said people who swam at beaches with poor water quality had a higher risk of contracting gastro.

media_camera The red dots show beaches with poor water quality on Monday January 2, 2017. Picture: Yarra and Bay.

The EPA forecast unsafe water quality at 16 of Melbourne’s bayside beaches in the lead up to the New Year.

kara.irving@news.com.au

@Kara_Irving