"The cut was deep, and kept on bleeding," she says. "I was quite a distance from the shore and my coach didn't know about my condition. I took off my sun-proof jacket to tie the wound and sailed back."
The 19-year-old was treated for her cut and took to the sea the next day, showing iron discipline that has seen her rise to the top in her sport. She carried on when other, lesser mortals would have quit: the competition started the day after her injury and she still decided to race.
"I had three stitches at the hospital and covered my injured leg in plastic wrap to avoid it coming into contact with the sea water. But the leg still got inflamed after the Day One race," says Hayley.
Her parents are nurses, and they were at home in Hong Kong, so her condition worried them. Hayley had to withdraw and fly home alone.
Hayley's tough self-discipline means that, despite being a champ on the board, she didn't miss a single lesson at university until last month, when she took time off to compete in the Asian Games.
"The absence made me worry about my studies as I didn't think I'd be able to catch up after missing one lesson, let alone a whole month of classes!" she says.
Hayley has racked up an impressive array of titles and trophies. She claimed the World Junior Champion title at last year's Youth Sailing ISAF World Championships. She also won two silver medals in multi-sport events, one at the East Asian Games last year and the other at the Asian Games last month.
Now she has her sights firmly set on the 2012 Olympics.
Unlike the Asian Games, the Olympics only allows two representatives from a country - one male and one female - to compete in the windsurfing competition.
"I need to fight for the ticket to the London Games and I think senior windsurfer Vicky Chan Wai-kei is smarter and more experienced than me. All I can do to catch up is practise more," says Hayley. Vicky represented Hong Kong in the 2008 Beijing Olympics and saw her career take off after Hong Kong legend Lee Lai-shan retired.
The Olympic Games qualification competitions start soon. Hayley must once again choose between her sport and her studies - she's in her first year at the University of Hong Kong studying English literature.
"I am in discussions with my school to see if I can suspend my studies and focus on qualifying first. I would like to finish my first year of study first, but the qualification competitions start early next year," she says. "I don't really know what I should do now."
Her current routine is punishing to say the least. Hayley finished her first exam on the morning of December 8, and then flew to Melbourne that night. After a few days of competition, she returned to Hong Kong for another exam.
No matter whether Hayley qualifies for the Olympics or not, the girl with the sail number "HKG 5" has certainly become a core member of the Hong Kong team.