More than 100 beachgoers have been left suffering with cold and flu-like symptoms after mysterious sea foam washed up on coasts across Australia.
Surfers have reported coughing, sore throats and blurred vision after entering the water.
Several beaches have been temporarily closed as authorities investigate the unusual foam, which has covered hundreds of metres of shoreline.
The strange phenomenon has coincided with fish deaths along the coast - marine animals including seahorses, fish and octopuses have all washed up on the sand.
The bizarre foam has killed fish and marine life across South Australia's beaches
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The foam has covered hundreds of metres along Waitpinga Beach, nearly 80km south of Adelaide in South Australia.
Parsons Beach, another popular surfing spot just west of Waitpinga, is also affected.
Visitors have noticed a visible "slick" on the water at both locations - and South Australia's Department for Environment and Water has temporarily closed Waitpinga and Parsons beaches while an investigation is underway.
Officials have pointed to a possible link between the foam and a microalgal bloom, which was likely triggered by hot temperatures, stagnant water and an ongoing marine heatwave.
The Department of Primary Industries and Regions is investigating what it called a "fish mortality event", while a spokesman said fish deaths can be caused by various factors including temperature, rainfall, water quality, disease or pollutants.
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South Australia's Department for Environment and Water has temporarily closed Waitpinga (pictured) and Parsons beaches
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These include respiratory and eye irritation, skin rashes, and possibly stomach upsets or flu-like symptoms.
"These symptoms disappear when the exposure stops or following washing in clean water," he said.
Ocean Watch Australia notes that "most sea foam is not harmful to humans" but warns that during algal blooms, "popping sea foam bubbles are one way that algal toxins become airborne".
The resulting aerosol can irritate eyes and poses health risks for those with respiratory conditions.