I’ve swum those waters many times, often out deep. In life saver training drills, in regular surf club swims out and around the buoys, I’m always scared about what might exist in the dimensions beyond the scope of my steamy goggles. Returning to the sand is my favourite part of each swim.

But to see vulnerability in this animal, it broke me. Because if there’s one thing I’m more scared of than sharks, it’s climate change.

A giant apex predator floundering and dying on a suburban beach is just the most recent example of an unprecedented marine die-off unfolding before our eyes in South Australia.

Since March, sharks have been stranded or washed up at Port Willunga, Moana, Ardrossan and Port Moorowie. Sick and dead sting rays, cephalopods, fish and even sea birds have accumulated on the Fleurieu Peninsula, Yorke Peninsula and Adelaide’s southern beaches. Thousands of stranded cockles formed a graveyard over the wide sands at Goolwa Beach.

On ANZAC Day, regular hiker Michelle walked 12km of sand from Foul Bay to Marion Bay on Yorke Peninsula.

“There were dead fish, including octopuses and small sharks, approximately every 50 metres. We saw hundreds; I’ve never seen this before in such numbers,” Michelle says.

The freshness of the animals indicated they had been brought in on the last tide.

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“It was upsetting, especially because quite a few were still alive. Some we tried to put back in the water, but I fear they probably died anyway,” she says.

That same week, I also witnessed dead rays, cuttlefish, puffer fish and terns at my favourite Marion Bay spot, Willyama Beach.

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The state’s mass deaths coincide with an oceanic bloom of microalgae known as Karenia mikimotoi. According to SA’s Department of Primary Industries, the bloom is linked with an ongoing marine heatwave, with water temperatures in April reported to be 2.5 degrees warmer than usual. Local scientists are currently collating data and performing autopsies on dead species to build evidence that could shift the relationship between algae and deaths from one of correlation to causation.

Back in Adelaide’s west, how are Henley locals handling it? It’s one thing to know that great whites are in the sea somewhere. It’s quite another to see one up close.

Ocean-lover Kim saw news of the stranded shark via social media, and rushed to Henley Beach to see it with his own eyes.

“It was a smaller shark than some, but still my heart was racing,” he says. “I can’t imagine how terrifying it would be to see an adult-sized one up close in the water.”

Despite his fears, Kim still had a sense of sadness.

“I felt sorry for the shark; it looked so helpless,” he says.  “The recent algal bloom seems to have changed the behaviour of sharks, as they are coming to shallower waters.”

Beck swims at Henley beach almost every day of the year.

“I have been involved in surf lifesaving since 2007, and I can honestly – and gratefully – say I have never personally witnessed a shark in the ocean,” she says.

“I felt very sad and sorry for the animal when I saw the news. Our oceans and sea life seem really fragile right now, which is worrying.”

Beck will continue to swim even with recent events.

“Ocean swimming connects me with nature. I never regret a dip in the sea,” she says.

Christine is also a regular at Henley. She said that while she usually regards ocean swimming as a relatively safe way to exercise, she does have a slight degree of hesitation given recent news.

“I usually hug the shoreline when I swim anyway, but evidence that the behaviour of marine life is slightly different, perhaps even erratic, at the moment has made me think twice this week,” she says.

“I’ll monitor the situation day by day and I’m sure I’ll be back in the water soon, taking every precaution I can – because it’s something I love to do, and it enhances my wellbeing.”

Christine does still have concerns over the health of our oceans over the longer term.

“With unusually warm waters and wind patterns altered, clearly climate change is a factor in the algal bloom and marine deaths,” she says.

“I’m concerned this is just the start of some dreadful environmental changes we are going to endure in the years ahead.”

The Intergovernmental Panel on Climate Change indicates that human activities have already locked in an average of more than one degree Celsius of global temperature rise, resulting in rising sea levels, extreme weather events and rapidly disappearing sea ice.

With 2025’s algal bloom and associated reporting on sharks as “lurking” in shallow South Australian waters and one having “flung” itself onto the beach, perhaps it’s time to rethink who is predator and who is prey.

Sarah Keenihan, PhD, is a science writer and patrolling member at Henley Surf Life Saving Club. She’s a member of the Environment Advisory Committee for Surf Life Saving SA and on the Advisory Board at the Environment Institute, University of Adelaide.