Jo Spargo arrived at her local beach in southern Tasmania as the sun was rising.
With two boisterous dogs in tow, she found the sand and waves covered with a jiggling blanket of sea foam.
"I was worried if it was safe for the dogs to be running in," Ms Spargo said.
"I was also wondering if it contained sewage from overflowing septic tanks as it has a brown tinge to it."
So, what is in sea foam? And was it safe for Ms Spargo and her dogs?
CSIRO algae scientist Anusuya Willis took a look at two takeaway containers of foam collected from Ms Spargo's beach.
What was in the sea foam?
Dr Willis scooped foam onto a dish and dropped sea water onto slides at her laboratory.
The screen connected to her microscope lit up and displayed a surprisingly diverse ensemble of shapes — some of which were wriggling.
"I'm seeing a lot of general organic matter, which you would expect," Dr Willis said as she examined the sample.
She said the organic matter would have come from a "mixture of all sorts of sources".
A lot would have been washed from land with the rain and be made of leaves, plant matter and soil.
Dr Willis spotted some tiny, harmless worms.
The sample also included a tiny algae called diatoms, although fewer than Dr Willis expected.
"Diatoms are single-celled organisms, so they're quite small … and are often a pretty golden-brown colour," she said.
"They are often at very high densities, especially at this time of year.
"In the springtime plants begin to grow and so do algae."
Dr Willis later collected her own seawater sample with her more specialised equipment and found it had large numbers of diatoms and another single-celled organism — dinoflagellates.
While some dinoflagellates have a reputation for being dangerous, the ones she found were harmless.
But why is it bubbly?
Diatoms and other living things produce a substance called "mucilage", which is a gluey secretion.
The mucilage-producing diatoms and the organic material washed in from the land are churned together in the surf.
"When it's all mixed up with the wind and weather and waves it can form bubbles," Dr Willis said.
She said the foam was a "soapy effect".
Was it dangerous?
The water was packed with life.
Dr Willis said that was normal for healthy seawater.
"It's completely harmless," she said.
"It's just dirty water.
"It might not be dirtier than it [seawater] normally is, so maybe it's not fair to call it dirty water.
"We can just see it because of the combination of events with the extra diatoms and the extra wind and rain we've had recently."
When is sea foam dangerous?
Derwent Estuary Program chief executive Ursula Taylor said it was best to stay out of the water for two to three days after heavy rain.
She said "that yuck factor" should be taken into account when deciding whether or not to swim in the water.
She said foam could also be the result of pollution.
"If it's not a natural process it can look quite different — it is often whiter and it can be fragrant," she said.
"Natural sea foam has a more earthy aroma."
Ms Spargo said she was relieved to hear that the sea foam her dogs were so obsessed with was safe.
One of her dogs found a puffer fish that had also washed in on the wind, so urged others to be careful.
Editor's Note (20/11/2022): Joanne Spargo is content director at ABC Hobart.
