World champion water skier Sarah Teelow has died from her injuries after a 120km/h fall on the Hawkesbury River, north of Sydney.
The 20-year-old suffered had been clinging to life with serious head and spinal injuries since Sunday.
Witnesses reportedly told police she hit a wake as the boat approached a bridge, causing her to fall heavily, shortly after the start of the Bridge to Bridge competition — a 112km race from the mouth of the Hawkesbury River to Windsor in Sydney's west.
Ms Teelow went into cardiac arrest but was revived by paramedics at the scene and flown to Royal North Shore Hospital, where she was placed on life support.
She remained in a critical condition on life support on Monday evening as late as 8.30pm, according to one hospital update, but sometime overnight she was pronounced dead.
Ski Racing Australia chief executive Kristie Middleton said: "The ski racing fraternity is deeply saddened by Sarah's passing and extends its condolences to her family."
Police are still investigating how Ms Teelow fell off her ski at high speed, including reports she hit wake created by another boat.
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Just two months ago Ms Teelow, who was based in Sydney, won the Formula 2 category of the World Waterski Racing Championships in the Canary Islands.
Afterwards she wrote about the challenges of the sport in a university blog posting.
"Water skiing, as a competitive sport, is a lot more than just how fast the boat goes," wrote Ms Teelow, a Bachelor of Human Movement student at UTS.
"You are limited by your ability and your fitness. It requires skill, balance, strength, endurance, determination and a lot of nerve."