Australia's Antarctic and sub-Antarctic expeditioners have braved icy waters in a traditional swim celebrating an important date on the Antarctic calendar.
Midwinter marks the shortest day and longest night of the year and represents a turning point for those living down south.
There are 90 expeditioners wintering at Casey, Davis, Mawson and Macquarie Island research stations this year.
At Australia's most remote station, Mawson, the sun is currently down all day, with the next sunrise not due until 29 June.
To celebrate the day, the team gathered on Horseshoe Harbour where an excavator cut through a metre of sea ice to create their sub-zero swimming pool.
"This is a tradition in the Antarctic calendar to celebrate the middle of winter and the return of the sun. It's madness, it's ridiculous, but it's what we do here in Antarctica," Station Leader Rebecca Jeffcoat said.
"It was minus 19 on the ice with a wind speed of six knots, so altogether it was probably about minus 25 with the wind chill factor."
"It's an Antarctic rite of passage to take a Midwinter swim and once is definitely enough."
"We have a great community of 15 here at Mawson and everyone had a safe and fabulous time."
All swims are conducted under medical supervision, with safety equipment and a warm towel close at hand.
The day is regarded as Antarctica's Christmas with chefs preparing winter feasts while expeditioners craft and exchange handmade gifts.
Australian Antarctic Division Director Kim Ellis thanked those spending a year away from their families and friends.
"Expeditioners are at the heart of Australia's Antarctic Program, they keep the lights on and our stations running," Mr Ellis said.
"Their work is critical in supporting our science and research efforts to understand and protect the frozen continent."
"Midwinter is a chance to reflect on some of the incredible accomplishments in the past year such as the delivery of Australia's new icebreaker RSV Nuyina."
"This year will also see modernisation works at Macquarie Island and the beginning of our Million Year Ice Core traverse, but today is all about having fun and letting our hair down."
