The Form Six student, who plays centre for Hong Kong's water polo team, decided to set up his own "school" mixed team - comprising boys and from different schools, who were also unable to play because they lacked teammates.
His efforts led to them playing at last November's 12th HKASA School Invitational Championships.
"Water polo is a seven-a-side team sport," Gary says. "Many Hong Kong students are water-polo fanatics like me, but can't take part because their schools don't have enough players to form a team.
"I didn't want us to miss out playing in the competition, so I thought we should form a combined team of players from different schools; that way everybody could join in."
Yet his plan generated such a positive response from his friends that he was able to form two teams. In the past, just a few schools that traditionally have had strong water polo teams played in the competition. But thanks to Gary's efforts, and the agreement of the Hong Kong Amateur Swimming Association, four combined and mixed-gender teams - including two set up by him - also took part last year.
Although the results of the combined teams did not count in the final rankings, Gary was delighted to finally be involved.
He was also pleased his younger brother, Kenny Fung Kong-chun, played in the tournament. "I taught him the basics of water polo; it was the first time he played [the sport]," Gary says. "Yet he scored a goal, which thrilled my family."
Gary became interested in water polo after competing for Tseung Kwan O regional swimming squad at a gala in Kowloon Park. "My swimming coach introduced me to Marcus Koo, captain of the Hong Kong water polo team, who asked if I'd like to try out for the team. It was frustrating at first. I didn't know how to pass or grab the ball. It was hard to fit into the team's play."
Yet thanks to his dedication, he slowly improved and the coach asked him to officially join Hong Kong's team last year, after the Lunar New Year. "I quit the swimming squad then," Gary says.
"I wasn't doing badly in swimming, but didn't feel I was improving as much as I wanted. Yet right from the time of my water-polo tryout, I knew it suited me more."
Last year, he was kept very busy competing - at two All China championships, an Asian Age Group tournament in Indonesia and the 13th Asia-Pacific Tournament in Hong Kong. He was also appointed captain of Hong Kong's B team.
The Hong Kong Diploma of Secondary Education candidate hopes to play in even more prestigious water-polo competitions after finishing his exams.
"Hong Kong's water polo team changes every four years, after each Asian Games," he says. "Many of the most experienced players left after the 2010 Guangzhou Games.
"My dream is to have the chance to compete at the 2014 Asian Games with my teammates."