Despite being brought up in Shanghai, surrounded as it is by the East China Sea, she had never seen sailing boats in the local waters or on television.
It is one of the many obstacles the Chinese sailor, who became an overnight sensation among the country's 1.3 billion population after London 2012, has had to overcome en route to becoming Olympic champion.
She only has 50% of her hearing, has little vision out of her left eye, and had a tumor removed from her knee just as her sailing promise was first being discovered.
'I've conquered quite a lot of difficulties,' she says somewhat modestly in near-perfect English -- she is currently studying in the UK, doing a two-year management course in Southampton, a port city on the south coast.
Her hearing problem is partially passed on from her father, who has lost 20-30% of that sense, and an unknown fever she had as a child that caused ear issues. Her poor eyesight was also genetic, passed on from her mother.
'I've got my eyes from my mother and ears from my father,' she says with a smile.
Then there was the tumor, which began with an ache in her knee and manifested into a constant pain before X-rays and then MRI scans discovered the growth.
'The doctor suggested operating but that was in 2002 and I was just 15,' she recalls. 'The doctor gave me the option and said, 'It's your decision,' but that it's better to remove it in case it turns bad like cancer.
'So it meant I had to take a year off, which was a pity as it meant missing the Athens Olympic trials, otherwise I feel confident I would have got in.'
But Lily, as she is better known and prefers to be called, was taught never to let such setbacks hinder her career ambitions.
A world champion in 2006, she won bronze in the laser class at her home Beijing 2008 Olympics. Her crowning glory of gold on British waters four years later earned her the honor of carrying the Chinese flag at the closing ceremony over far more established names.
'After London, the Chinese media really put me under the spotlight,' she explains. 'I guess not only because sailing is so strong in the UK and I got to go there, but because of the difficulties conquered.
'Sailing is nowhere near a popular sport in China but the media did a fantastic job and, for me, why wouldn't I cooperate to make the best of that opportunity for the sport?'
In China, Xu is the equivalent of Ben Ainslie, the British sailor who is a four-time Olympic champion and now heads up one of the leading America's Cup challengers to Team Oracle USA.
The pair were both awarded sailor of the year at the end of 2012, a year in which Xu was named Chinese sportswoman of the year, beating such luminaries as teenage swimmer Ye Shiwen -- a double gold medalist in London.
In the UK, however, you wouldn't know that she warrants such superstar status. On campus in Southampton, she walks around relatively unnoticed; at the recent Extreme Sailing Series event in Cardiff where she acted as an umpire for the first time in her life, again she was barely recognized.
Back in China, it is a different matter, one she relishes because of the increasing profile of her sport.
'I remember an optimist (a type of sailing class) coach came to my primary school,' she recalls. 'At that time I was doing swimming every day for two hours after school, and the coach approached me.
'My reaction was, 'What is sailing?' -- we didn't have any image in our minds as we'd never seen it on telly, even on the seaside. Now that's changing with world-class marinas along the coast.'
Clearly a natural on the water, she was sent to a training camp where she was picked out in the top three before being brought into the Chinese sailing program, which meant relocating hundreds of miles away from her parents.
'I remember my Dad said, 'Lily, this is your decision but do the best you can and never give any chance that you will regret that decision.' '
Her Olympic ambitions have been realized -- she will not seek selection for Rio 2016 -- and Xu now wants to branch out with her sailing.
Despite all her success, she sees herself as a fraud in some ways in the sailing world.
'I feel a bit ashamed as an Olympic sailor that I only know how to single-handed sail a dinghy,' Xu says.
'I want to try yachting, big boats, multihulls and offshore. I want to explore the world and I want to sail forever, it's a lifetime sport.'
She admits that, with her hearing, communication is a difficulty in a team sailing environment but she has already been on board as a guest in the Extreme Sailing Series and with Volvo Ocean Race crew Team SCA.
Her decision to study in Southampton was aimed with a view to doing more sailing but her lectures clash with the university's Wednesday afternoon boating activities, so such pursuits are on hold for now until she graduates with a Master's degree in international management next year.
'I'm still aiming for professional sailing after graduation. I want to be a competitive sailor.'
Where that is she has no idea, but the drive remains.
Read: China's Volvo Ocean Race team
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