The Shire of Esperance has urged members of the public and pet owners to avoid the area between Taylor Street Beach and Port Beach following an algal bloom.
Shire environmental health officers have placed signage in the affected areas and are monitoring the situation.
A similar warning was issued for the same area in February, 2019.
The algae, more commonly referred to as red tide or sea sawdust, is easily identified by a yellow, brown surface scum with an oil slick appearance.
The water surrounding the algae may change to a pink or pale green colour as it begins to decompose.
Trichodesium algal blooms have occurred sporadically at various locations along the state's coastline and tend to be moved by ocean currents.
The Department of Health advised that recreational activities such as swimming, and shellfish collection be avoided in the area as contact with the bloom could result in skin irritation.
The algae is a naturally occurring event and was likely to have been swept in with winds and tides.
It is expected to move away from the area in the same way it has done in the past.