Friday's 7.42am sunrise plunge into the River Derwent in Hobart marks the passing of the longest night of the year.
The swim has been expanded from 2000 to 3000 participants after increased demand.
It's a far cry from the inaugural swim in 2013 which featured just 300 swimmers and needed a special permit to go ahead.
"Every year we are inundated with messages from disappointed punters who missed out on a spot," Dark Mofo executive producer Melissa Edwards said.
The festival has worked with Surf Life Saving Tasmania to boost capacity.
A nippy 6C minimum is forecast for Hobart on Friday, as well as cloudy conditions, light winds and the chance of showers.
Dark Mofo, which wraps up on Sunday, ran a reduced program in 2024 so it could find a more sustainable financial model.
The Tasmanian government has committed $7.5 million to the music, food and art event over three years.
The festival has made a name for itself by courting controversy and in 2018 drew the ire of some by installing inverted Christian crosses along Hobart's waterfront.
9°C