It may be more than 40 years ago, but the first day of his Outward Bound Singapore (OBS) experience is still vivid for Mr James Lam.
"When we reached Pulau Ubin, we were told to drop our bags and go for a run," said the 64-year-old.
"I had no idea how long the run was... More than 100 of us were just following the warden through the jungle. After the run, he gave us a welcome speech."
For Mr Lam, then an army regular, OBS was like a "boot camp". "Training was as tough as, or more so than, the army," he recalled.
He said on a visit last month to OBS on Pulau Ubin: "It's my first time back at OBS and everything has changed." He added: "Last time it wasn't as clean, well maintained and modern."
OBS' outdoor education programme is held on two campuses on Pulau Ubin, with a new campus on Coney Island coming up in three years.
With its uneven rocky surfaces, sandy slopes and dense forests, OBS was a real training ground, said Mr Lam, now a freelance special needs therapist. The daily routine of the 21-day course he attended started as early as 4.30am, with an hour of basic exercises such as rope climbing and sprinting, followed by flag-raising and singing of the National Anthem, then breakfast.
Running was part of the daily training. "Our warden told us this, 'Don't give up. No matter how exhausted you are, you must still crawl towards the finishing line,'" he said. Some of his batchmates lost so much weight that their pants became loose, he added.
His time at OBS taught him endurance and perseverance. "You can do things you thought you couldn't do," he said.
From climbing granite hills and walking on two ropes to jumping into the sea from a height and learning to sail on a viking ship, the three weeks were memorable.
"It took 20 of us to row the ship with a giant long oar, not like today's kayak," said Mr Lam, who is married with two daughters.
An unforgettable experience was a night walk with moonlight as a guide. "The instructor told us to close our eyes for five minutes then open them," said Mr Lam. "Our eyes adjusted to the darkness, and we could see our surroundings."