SINGAPORE - He is 16 and is already a veteran of guided tours at biodiversity haven Chek Jawa on Pulau Ubin.
Dunman High School student Choo Yi Feng started conducting solo tours for groups of about 15 when he was 12, after a year of training from other guides.
But what made someone so young so passionate about the environment?
Yi Feng said it started after a trip to Underwater World in Sentosa, when he was three.
"I started reading books and watching documentaries about sea animals," he said.
At the age of eight, he visited Chek Jawa, and he knew then he wanted to be a guide.
Despite being told he was too young, Yi Feng continued to learn as much as he could about Chek Jawa's wildlife. On his next visit there, he volunteered as a guide again. He was only 11 then.
The answer from the lead volunteer guide was "yes".
He might know a lot about the wildlife, but it wasn't all smooth sailing for Yi Feng, especially on his first time leading a tour.
"Back in 2009 when I first started, I was so nervous that I missed out several spots on the boardwalk," said Yi Feng.
Fortunately, he had help from some of the more experienced volunteers.
"Because of the age gap, it's difficult for me to join their adult conversations," admits Yi Feng.
"They usually just ask me about school and we discuss marine wildlife." Five years into the job, Yi Feng has no intention of stopping.
Little surprises, like spotting an octopus - an elusive creature - keep him hooked.
"The experience each time is different, with different groups of tour participants bringing different challenges," said Yi Feng.
"When dealing with the (very young), for instance, I try to not to use complex words."
"And because they can get a little too enthusiastic, I'll remind them to be gentle when handling small marine creatures."
For each two-hour tour, Yi Feng guides a group of about 15 people along the 1.1km-long Chek Jawa boardwalk, pointing out different marine organisms and sharing interesting trivia.
Participants are often surprised by this secondary four student's extensive knowledge on local marine wildlife.
"To prepare myself for tours, I read up a lot on marine biodiversity."
"And whenever a book about Singapore's marine wildlife is published, I'll be sure to buy it," he said.
In 2011, Yi Feng had the honour of taking President Tony Tan Keng Yam, his wife and grandson around Chek Jawa.
"It was intimidating with a lot of press following us around," he recalls, "But the President was friendly and interested. We even chit-chatted about my volunteer experience."
Since he spends so much time volunteering on Chek Jawa - sometimes making up to five trips a month - does Yi Feng have time for his books?
Yes, he says, partly because he is in the Integrated Programme and does not have to take the O levels.
"Tours don't take up the whole day. And because I'm passionate about it, it doesn't feel tiring."
Looking to integrate his passion for nature with the school curriculum, he plans to sign his school up for NPark's Greening Schools for Biodiversity programme, an initiative to attract more biodiversity in schools.
He wants to pursue Environmental Studies at the National University of Singapore in the future.
NParks invited Yi Feng to share his experience as a volunteer last year at its annual Appreciation Day, held to thank NParks' 800 volunteers, The Straits Times reported.
Yi Feng also appeared on the cover of NParks' Annual Report 2012/2013.
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