He was one of the pioneer participants at Outward Bound Singapore (OBS) in 1967, and 50 years later, Prime Minister Lee Hsien Loong still recalls vividly the 17 days spent at the adventure school.
Then 15 years old, he and his peers went canoeing and sailing in the sun and the rain, and spent a day hiking from one end of Pulau Ubin to the other.
They also did orienteering and "often got hopelessly lost", he recalls.
Speaking at an event to mark the golden jubilee of OBS, he said that those experiences pushed them to the limits.
He said: "My coursemates and I found OBS a challenging experience, but we also enjoyed ourselves immensely. We came from different schools, different social backgrounds, different races, boys and girls. We made friends quickly.
"We also had to get fit, to learn new skills, to encourage one another along on exercises and adventures."
He added: "Those 17 days had a lasting impact on us, and certainly on me."
OBS ended a year-long celebration of its 50th anniversary with the ceremonial unfurling of the OBS Indiana's sail on Pulau Ubin yesterday.
Those 17 days had a lasting impact on us, and certainly on me.
PRIME MINISTER LEE HSIEN LOONG, on his experience as a pioneer OBS participant.
The event marks a new chapter for the adventure school, which has seen more than 500,000 Singaporeans participating in its activities since it began in 1967.
Currently, about 14,000 young people take part in OBS programmes each year. This number is set to more than triple to 45,000 from 2020, when a new OBS campus on Coney Island is expected to be ready.
At the event, Mr Lee, together with other OBS alumni, also took the helm of a cutter sailboat headed for Coney Island from Pulau Ubin. He later mounted a nautical wheel at the site of the new OBS campus before visiting its facilities.
Mr Lee, who had also visited OBS 10 years ago on its 40th anniversary, said that its mission to develop rugged young people is even more relevant now.
"Our children are growing up in a much more developed and urbanised environment," he said.
"There are fewer opportunities to rough it out in the outdoors, and shelter from bad weather is usually just a few steps away. Nowadays, parents, teachers and schools are also more protective."
When children go camping now, they often sleep in the school hall or classroom, or sometimes on the Marina Bay floating platform, he added. "So that sense of nature - the outdoors and adventure - is not quite the same."
Mr Lee noted that outdoor adventure learning is useful in imparting life lessons, such as teaching young people to be adaptable, which are hard to teach in the classroom.
To mark its 50th anniversary, OBS, part of the National Youth Council, held a series of events this year. They included a homecoming where some 500 OBS participants, instructors and staff - past and present - relived memories and took part in water and height activities, and nature and heritage walks.
OBS offers activities that include a mix of land, water and height elements. Trainees learn skills such as kayaking and cooking outdoors.
Yesterday, Mr Lee also launched the adventure school's 50th anniversary book, which includes personal stories from participants, instructors and partners through its years of youth development.
Among those who benefited from the adventure school was St Patrick's School student Jonas Koh, who attended OBS last month.
For the 15-year-old, participating in the OBS programme helped him to step out of his comfort zone.
"Before this, I've never slept outdoors before. So it was an eye-opening experience and it taught me to appreciate the simple things that I have," he said.