An ill-timed breath of air was the difference between finishing first and second in yesterday's Schools National C Division boys' 400m freestyle final but for runner-up Sheldon Tan, there was no trace of disappointment as he savoured yet another milestone.

The Evergreen Secondary School student had finished fourth in the same event last year and received a medal, which was the Woodlands school's first for swimming at the National School Games.

Sheldon doubled that tally for Evergreen at the OCBC Aquatic Centre when he touched the wall in 4min 17.33sec, just 0.12sec behind Anglo-Chinese School (Independent) swimmer Zacc Lee (4:17.21). Marc Lim of Raffles Institution was third in 4:30.23.

Sheldon, 14, said: "I was just trying to hang on and bring up my stroke rate. Towards the last five metres, I was not supposed to breathe. But I felt breathless and too tired, so I breathed and I think that cost me the race.

"My target for myself was 4:14, but I didn't manage to hit that so I'll work harder."

Despite acknowledging there were areas of improvement, he was glad to have lowered his time.

"I felt joy (after the race) because last year the gap between me and Zacc was about 1sec. This year, I managed to close it up," said Sheldon, who posted 4:30.56 last year while Zacc was third in 4:29.51.

Swimming is not an official co-curricular activity (CCA) at Evergreen, though the sport is recognised as an external CCA. Sheldon, whose official CCA is cross-country, is one of the two school swimmers at this year's meet.

"I just felt very happy because it had never been done before and I was the talking point of my whole class. I think even the Secondary 2 cohort last year knew about it," said the teenager, adding that he felt like a mini-celebrity after last year's achievement.

The 1.73m Sheldon initially found it "boring" when he first learnt to swim at age five, and grew to love it only when he was in Primary 5 after spending more time in the pool.

"I just like the feeling of being in the water," said the former Endeavour Primary School pupil, who also took up swimming as an external CCA there.

He attributed his improvement to the amount of training he has been doing - eight times a week with swimming academy X Lab, which he joined in Primary 6.

He added: "Coming into the meet last year, I didn't really have that serious mentality. All I thought about was playing the whole year.

"I noticed the more I trained, the faster I became and the more I improved, so I took it more seriously."

In the A boys' 400m, RI's Glen Lim swam 3:55.78 to better Jerome Kwang's 2015 time of 4:11.62 and now owns all the three division records.

It is still off his national record of 3:52.64, which he set last month.

The 17-year-old said: "I'm quite happy considering this week has been a tough week of training (with the national team). I'm still trying to adapt to the new training plans so it feels pretty good."