Her legs and wrists were sore and her elbow was bruised, from the inside to the out, and she was desperate to sleep.
But she escaped sunburn and chafing, thanks to a mix of potions and lotions including sunscreen, zinc, lanolin, vaseline and creams.
"I think I am worse than I expected. I’ve been watching some of the videos when I finished at the Clyde Dam and I was talking really slowly. It sounds like I was affected by the cold but I wasn’t. It was extreme exhaustion.
"I was physically sick last night and everything is sore to touch today," she said on Monday.
"I am having a weird reaction with my thermostat control. My feet are freezing cold and my legs are burning hot ... It must be a physiological overload," she said.
Her Lake Dunstan swim from the Clutha River inlet to the Clyde Dam is believed to be the first by a non-wet suit swimmer.
Mrs Fairbairn’s big day out has raised at least $4000 so far for Otago Rescue Helicopters, an organisation she and her late husband, Darryl Fairbairn, supported and worked with when they were surf life savers.
The swim took her about 13 hours and 35 minutes to complete, starting about 8.30am and finishing about 10pm. A southerly headwind slowed her progress in the second half of the swim.
The lake temperature on Sunday ranged between 17 degC and 20 degC.