The City of Rockingham issued a health warning and closed part of the popular foreshore on Friday after high bacterial levels were found.
Beaches between Hymus Street and Palm Beach boat ramps were closed as a precaution.
Signs with the warning “This water may cause ill effects to humans and animals. No direct water contact activities,” were placed at the entrances to the beach.
People are warned not to swim, jetski, windsurf or fish in the area.
In a post to social media, the City wrote it would reopen the beach once levels have returned to normal.
As part of the Department of Health’s bacterial monitoring program each Perth metropolitan swimming beach is given a temporary grade.
The Hymus Street location currently has a fair grade and is safe for swimming “most of the time”.
A fair grade indicates that elevated bacterial levels can sometimes make the area unsuitable for swimming.
“Elevated bacterial levels are likely due to animal pollutant sources e.g. bird faeces, and from contaminants flushing into the water following rainfall,” the Department of Health website reads.
Last week the ABC Perth named Rockingham Foreshore Perth’s best beach from a list of five.
The City of Rockingham has been contacted for more details.