SINGAPORE - The leopard whiptail ray that killed an Underwater World Singapore (UWS) senior diver last year had never displayed aggressive behaviour and had adapted very well with its environment.

But when Mr Chan Kum Weng, 62, and the other divers tried to catch the stingray at around 2pm on Oct 4, 2016, it suddenly attacked him with its venomous barb that originated near the base of its tail.

In an inquiry into Mr Chan's death on Wednesday (March 1), the court heard that the barb pierced his chest and he was pronounced dead about 1½ hours later.

State Coroner Marvin Bay, who found his death to be a tragic misadventure, said: "As stingrays are generally shy creatures, their initial reaction to a threat would be to swim away.

"Cornered or surprised rays would nevertheless resort to attacking a perceived threat."

Mr Chan, who worked for UWS for 26 years, and his fellow divers had been tasked to move the stingray after the Sentosa attraction closed its doors last June.

It was one of four leopard whiptail rays that had to be transported to Malaysia on Oct 7, last year.

Mr Chan and his team successfully herded three of them into tank.

They then dived into another tank where the fourth one was held and proceeded to herd it to a shallower area so that it could be caught with a net.

Mr Chan suddenly shouted before collapsing.

Sensing that he was in distress, the divers in the vicinity attended to him and lifted him onto a walkway to the quarantine section and called emergency services.

When they cut his wet suit, they saw the 22.5cm long barb with serrated edges protruding out of his chest.

Paramedics from the Singapore Civil Defence Force arrived at the scene soon afterwards and he was rushed to the Singapore General Hospital where he died.

Coroner Bay said: "Animal handlers must maintain a state of complete mindfulness, care and focus when handling a wild animal.

"It should be evident from Mr Chan's case - which has very sad parallels with that of famous wildlife personality, Mr Steve Irwin - that expertise, skill and experience will not invariably insulate an individual from such animal-inflicted harm."