|Welson however failed to qualify for the top-16 to reach the semi-finals. - AZHAR MAHFOF / The Star|
The 19-year-old clocked 1:47.67 to finish sixth in heat three at the Olympic Aquatics Stadium on Sunday. He set the national mark at the Singapore Age-Group Championships in March.
Welson was hoping to set a new mark here with the stiffer competition, but he failed to do so.
"I am disappointed. I could have done better," said Welson, who finished 26th overall in the 47-man field.
Earlier on Saturday, Welson clocked 3:51.57 and failed to beat his 3:50.33 national record. He was 34th overall in the 50-man field.
Phee Jinq En was the other Malaysian swimmer in action on Sunday and she left the pool in tears in her Olympic debut.
Competing in the women's 100m breaststroke, the 19-year-old clocked 1:10.22 to finish second in heat two. It was way off her national record of 1:08.65 which she achieved at the Malaysian Open in May this year.
It was Jing En's only event here while Welson still has the 1,500m on Aug 12.