A record 1,537 people in Tasmania have marked the winter solstice with a nude swim in the River Derwent, as Antarctic expeditioners plunged into icy waters at Casey Station.
Australians have marked the winter solstice - the shortest day and longest night of the year - with bare bums and icy plunges.
In Tasmania, a record 1,537 people swam nude in the chilly River Derwent, including 74-year- old Graeme Mineall who did not let a wheelchair stop him from celebrating.
"It wasn't as cold as I thought it would be. Was colder when I got out,” said Mr Mineall, who has multiple sclerosis.
Mr Mineall was helped into the water by carers Sarah Franks and Angie Cassidy who went into the 14C river with him.
"If you can do it, try. It's worth effort. It was a marvellous experience."
With the air temperature hovering around 7C, the crowd dropped their towels and made a beeline for the water when the sun rose at 7.42am.
Most let out shrieks, others had a seemingly comfortable paddle.
Wearing nothing but red swimming caps they returned to shore to fire pits and white towels - in strong supply after last year's shortage left some bare-bottomed.
"We over-ordered this time," organiser Kate Gould said.
Liss Finney said it was a great way to mark her 26th birthday.
"It was exhilarating,” she said. "Your skin starts burning a little bit from the cold and it's really hard to catch your breath.
The crowd of 1,537 beat last year's record by several hundred.
Icy plunge honours early explorers
The tradition of icy plunges was also observed earlier this week by Australia's Antarctic team, who braved -22C temperatures and plunges into the ocean.
The practice continues a winter solstice tradition that began with early explorers, such as Sir Douglas Mawson.
Their midwinter celebrations at Australia's three Antarctic research stations and sub-Antarctic Macquarie Island also include a feast, exchange of handmade gifts, midwinter play and messages from home.
Winter solstice marks the shortest day of the year and means the journey towards summer has begun.
Myths on how seasons change still exist: astrophysicist
Meteorologists and astrophysicists shared their wonder.
Astrophysicist Professor Tim Bedding says myths about how seasons change still exist.
"The most common misconception people have is that summer and winter happen because the earth is closer in summer and further in winter," he told AAP on Thursday.
"You'll still find well-educated people who think that."
But Professor Bedding said the earth's journey around the sun is almost circular and the seasons actually occur because the earth's tilt causes the northern and southern hemispheres to receive varying exposure to the sun during its year-long orbit.
"We get sunlight but we don't get it for as long and when it does get to us it's shining more at an angle, so the sun is lower in the sky and the heat from the sun is spread over a bigger area," he said.
Tourism and Events Queensland tweeted about the benefits of the long night.
Air New Zealand also shared its view of the positives.
Pictures of barren winter trees were the order of the day for some social media users.