Hundreds of people have braved the chilly waters of Hobart's River Derwent for the city's annual nude swim to mark the winter solstice.

With temperatures hovering around 1 degree out of the water and 11 degrees in, the solstice swim brings to an end 10 days of Hobart's third Dark Mofo winter festival.

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Splashing in at sunrise on Sandy Bay beach, the crowd was greeted with a bitter blast, with most swimmers staying submerged for only a moment or two, only to be hit onshore by an air temperature of just 1 degree Celcius.

About 1,100 people registered for the event, but organisers said the cold weather may have turned off a few reluctant swimmers.

The final head count was 752 skinny dippers.

Sydney twins Stephen and Michael Samson took the plunge to celebrate their 50th birthday.

"We turned 50 in December," Stephen said.

"Instead of doing something like bungy jumping or skydiving we thought we'd do a nudie swim."

The twins said they felt invigorated after the breathtaking swim.

"Once the drum beat got going, got you psyched up, bolt straight in and it was fan-bloody-tastic," Stephen said.

"We want to bring a whole bunch of mates next year," Michael added.

After taking warmth from the fires on the beach, one swimmer had some advice on how to adjust to the cold.

Sorry, this video has expired Nude solstice swim tests resolve ( Kieran Jones )

"Come here first with not much on so that when you're in, it's not so much of a shock," she said.

"Then once you're in, just swim and scream!"

Sandra Gadsby from the Kingston Surf Life Saving Club said the swim was too much for some.

"We did have to help a couple of people," she said.

"I think it was mainly asthma, with the cold temperature of the water [some people] had a little bit of difficulty breathing so a couple of people got a little bit of help, but that was all."

The winter solstice is an astrological event marking the shortest day and the longest night of the year.

It also coincides with the northern hemisphere's summer solstice, an event marked by thousands of people at England's Stonehenge.

Antarctic expeditioners honour traditional solstice swim

If a dip in Hobart's icy waters in the middle of winter was not cold enough, a group of Antarctic scientists also stripped off for swim honouring a long-standing tradition.

The midwinter swim has been a celebratory activity in Antarctica since Mawson and the early days of exploration on the icy continent.

At midday on Sunday, in sub-26 degree Celsius temperatures, 13 expeditioners from Australia's three Antarctic stations went for a dip in the icy sea water through a custom-made ice hole.

A couple of the swimmers managed to do a lap or two but most could only manage 30 seconds in the water before being helped back into a preheated container nearby.

Australian Antarctic Divisions officials said all of the swimmers were well and enjoyed the customary mid-winter feast after the swim.