Even when he knew he was risking his life, Mr Zhai Hailei jumped in to save his friend.
Sadly, Mr Zhai, 25, and Mr Yang Zhonghua, 37, died days after being found by other colleagues in a waste-water pit.
Both Chinese nationals were employees of Nam Heng Leather Dyeing at Tai Seng Industrial Estate, near Upper Paya Lebar Road, where the accident happened on Dec 26 last year.
At work, Mr Zhai and Mr Yang would often spend time chatting during their breaks.
On their days off, the two were just as inseparable.
After the accident, the good friends died within hours of each other on Jan 4 - Mr Yang at 10.55am and Mr Zhai at 8.30pm.
In his findings yesterday, State Coroner Marvin Bay said the deaths were "misadventures of an industrial nature".
He said Mr Yang most likely fell into the water, which was 2.5m deep, as he was disorientated by the harmful hydrogen sulphide fumes in the vicinity while "perched precariously" above the water pit (also called a sump).
Mr Bay said: "(Mr Zhai) perished as a result of his valiant, but ultimately futile, attempt to save his co-worker and friend."
On Dec 26, Mr Yang had reported for work as usual at 8.30am and company foreman Chew Hock Seng, 61, told him to collect two plastic sieves that were hooked onto a metal beam directly above the sump.
A closed-circuit camera captured Mr Yang entering the sump area at 8.48am and he disappeared soon after.
Suspecting that he could have fallen in, Mr Chew asked Mr Zhai to search the area.
The camera captured Mr Zhai near the sump and he, too, disappeared moments later.
After five minutes, a panic-stricken Mr Chew alerted all the other workers to search for the two men.
He told his manager, Mr Ang Keat Hong, 39, about the situation and the younger man went to the sump to look for the workers.
As Mr Ang was removing a makeshift platform made of wooden planks there, he caught sight of an unconscious Mr Yang in the water.
The Chinese national was pulled out and his friend, who was also unconscious, was spotted minutes later.
Both men, who were wearing slippers instead of anti-slip safety boots, were rushed to Changi General Hospital but died eight days later.