Two Chinese tourists and a local dive instructor died in waters off Malaysian Borneo with the cause thought to be due to fish bombing.
The news of the incident has shocked locals and has worried the diving industry.
Fish bombing is outlawed but enforcement is lax due to the relatively remote offshore location.
Police said it is being investigated as a potential murder case and the perpetrators are being hunted.
It is a ‘life or death’ issue which needs to be outlawed once and for all, said interim head of marine at WWF Malaysia, Monique Sumampouw.
She called for a big crackdown to stop ‘illegal, unreported and unregulated’ fishing in the area.
Tourism, arts and culture minister Mohamaddin Ketapi also condemned the practice of fish bombing.
Mohammaddin said he was awaiting a full report on the incident near Kulapuan Island off Semporna, and stern action will be taken, including stiffer penalties imposed.
It is is thought to be an area where fish bombing is still rife due to a lack of a police presence.
He added further measures will be taken to safeguard the reefs and protect divers.
"I express my condolences to the families of the victims," he said in a statement.
