Queensland sailor Lisa Blair has been forced to abandon her attempt to become the first woman to circumnavigate Antarctica solo after her mast broke in treacherous conditions in the Indian Ocean.
The 32-year-old issued an international radio distress signal about 3am AEST on Tuesday while battling 40 knot winds and a seven-metre swell nearly 900 nautical miles south of the South African city of Cape Town.
Ms Blair, who was on day 72 of her journey, had a few hours to wait before daylight when she would be able to properly assess damage to her boat, a spokeswoman told AAP on Tuesday morning.
The spokeswoman said Ms Blair's life wasn't in immediate danger and her team were figuring out the safest place for her to motor to.
"It brings this dream to an end unfortunately, it is impossible for her to continue with the boat in its current state," she told ABC radio.
"She's in swells somewhere between seven and nine metres, so we're getting to two and three storey building swells,
"Her mood is a mix of disappointment, but of course adrenaline and (she's) very tired, as she works to ensure both her boat and herself are safe."
The journey aimed to raise awareness for climate change, with Ms Blair feeling compelled to act after seeing the impact it was having on the ocean after she began sailing in 2005.
She renamed her boat Climate Action Now for the record-attempt, painting it with post-it note messages from supporters which outline commitments they have made to support climate action.
Ms Blair was also attempting to break the record of circumnavigating Antarctica set by Russian Fedor Konyukhov, who made headlines last year when he went around-the-world in a hot air balloon in record time.
Ms Blair had just entered the Indian Ocean before disaster struck, which was the last sea she had to cross before returning to Albany, where she set off from in January.