Natasha, 19, a Form Six student from Diocesan Girls' School, in Jordan, who won last year's women's New World Harbour Race, is Hong Kong's youngest female competitor at the London Games.
"It's great to finally qualify," she says. "I was born in London, so to be able to compete in my birthplace is a special feeling."
She first tried to qualify for the Beijing Olympics at 15, in the 10km open-water race. The event, officially known as marathon swimming, made its debut at the 2008 Games, but Natasha failed to win a place.
However, her frustration inspired her to make immense improvements in her sport. She won her first major title at the third Asian Open Water Swimming Championships in Hong Kong in 2009, then claimed a bronze in the same competition, in Oman, a year later. She also won a silver medal in the women's 1,500m at the 2009 East Asian Games.
"I put my studies on hold after the 2010 Asian Games to focus on my swimming," Natasha says. "I train seven days a week, including gym work and morning training, at Hong Kong Sports Institute and [there are] afternoon sessions at Kowloon Park pool. The training programme of Chung Yuen - my coach over the past 14 years - is known as the toughest in Hong Kong."
Natasha started swimming when she was five and chose to compete in breaststroke events. She says: "I changed to long-distance and open-water swimming when I was 14. I thought it was my best chance to break through in the sport."
As qualifying for the London Games neared, Natasha's form began to wane. She failed to win an open-water medal at last year's Asian Championships, then missed out on a qualifying spot for the first London Olympics time trial in Shanghai.
"So I changed my plan and tried to qualify for the 800m freestyle event," she says. "But, after two time-trial events this year in Hong Kong, I was still 0.8seconds outside the qualifying standard. So my chances looked dim."
Yet just when her Olympic dream looked over, a "window" of opportunity opened at the Fina Olympic 10km Marathon in Setubal, Portugal, in June - the last Olympic qualifying race. She says: "In this event, of six 1.6km laps, I needed to finish in the top 10 to qualify - or be the top Asian swimmer among the remaining athletes to win one of five places reserved for each of the different continents. My goal was to take a reserve place."
On the last lap of the race, Natasha overtook five swimmers and then, right before the finish, she was level with a Japanese swimmer, Yumi Kida.
"I was really nervous when I saw her," Natasha says. "I thought both of us couldn't finish in the top 10 and, if she finished before me, she would take the place reserved for the Asian continent, so I gave everything I had left to go past her and stay in front till the end.
"I came 12th, but some swimmers who finished ahead of me missed out because other swimmers from their nations had already claimed the single qualifying place.
"So I actually was named the ninth swimmer to directly qualify - without having to wait to hear I'd got a reserve place. It was beyond my wildest hopes. Yumi also directly qualified, too, in 10th."
Since securing qualification, Natasha has had no time to relax. She is busy training in Harbin, in Heilongjiang province, and returns to Hong Kong next week.
She is also busy trying to get tickets so that her family can watch her compete at the Olympics.
"I didn't expect to qualify - I'd tried and failed before - so by the time I checked on ticket sales for the Games for my family, all the tickets had already sold out. Now I just hope someone can help me out," Natasha says.