The Cambodian Mine Action Centre yesterday successfully completed the underwater removal of a 500-pound (227-kilogram) aerial bomb recently discovered in the Mekong River in Kandal province, a historic first for a country that has dealt with thousands of leftover explosives from past conflicts.

The inaugural underwater mission comes after two years of intense preparation for CMAC’s first dive team, none of whom even knew how to swim properly prior to their training.

CMAC, in partnership with the Golden West Humanitarian Foundation – a charity devoted to assisting mine-impacted countries and sponsored by the US State Department – conducted yesterday’s recovery and defusing operation after Yor Deuob, a local fisherman from Lvea Sar, discovered the MK82 bomb two weeks before when it got tangled in his fishing net.

“One fisherman approached our team and they said, ‘We have something that’s getting caught in the nets, and we think it’s a bomb.’ The dive team got the information, we came out, we did a dive and we confirmed that it was a bomb,” said Mike Nisi, chief of underwater operations for Golden West.

Whittled down from about 40 initial volunteers, the dive unit, based in Kampong Chhnang, trained rigorously in the lead-up to the mission. In addition to an intense physical-fitness regimen and months of careful planning, they were subject to practice dives in a “black water environment” – in which their goggles were spray-painted to simulate zero visibility – in order to teach them to depend on their other senses during missions in dark, murky waters.

“[This] is some of the hardest, most dangerous diving there is,” said Allen Tan, Golden West Cambodia country director. “And that’s separate from the bomb.”

The team was tasked with fishing out the MK82 from a river that has 10 centimetres of visibility on a good day. One of the most common aerial bombs on earth, it has a blast radius of about 200 metres. This particular bomb was likely dropped during the Vietnam War era. It either didn’t receive the physical force required to detonate, or it was defective from the get-go – nobody’s sure, said Tan.

Still, he added, “this [was] a live bomb”.

Due to the uncertainty over the bomb’s condition, the whole operation was done at a distance. Though divers conducted necessary underwater procedures – attaching equipment, scanning the bomb with handheld sonar – they were out of the water when the explosive was ultimately dislodged from its resting place. Though largely contained under the water, the blast would have still been a threat to those in its immediate vicinity. As such, local police cordoned off the area to locals and assisted in the operation to ensure the community’s safety.

In the actual removal, the UXO was raised via a remote lift bag – essentially a large balloon. Once it reached the surface, the bomb was towed to shore for recovery.

John Wright, the chief engineer at Golden West, rigged a wirelessly controlled band saw in order to cut into the bomb and defuse it from a safe distance. The saw, which removed the nose and tail of the device, was operated remotely from a computer and a wireless transmitter.

Ultimately, the bomb was successfully cut, and the potentially lethal explosive was rendered harmless. Now it will be brought to Golden West’s Explosive Harvesting Program, where its contents will be recycled to produce explosives that will clear landmines in the future.

“You need explosives to destroy explosives,” Tan said. “It’s turning the weapons of war into tools of peace.”

Sok Chenda, the leader of the CMAC dive team, stoically acknowledged his group’s accomplishment following the mission.

“It went well,” he said. “Fishermen could have died. They don’t have training, and we do, so it’s no problem [for us].”

But despite the bomb’s removal, local residents’ concerns have not been quelled. Sam Sorn, a 77-year-old villager, had never heard of bombs in the area prior to the removal. But now that she knows, she expressed fear that her children may find one in the future and be killed.

Tan admitted that his organisation is unsure about just how many unexploded bombs lurk beneath the surface in Cambodia’s waterways. But rather than focus on every unexploded bomb or sunken munitions ship that may be present, he said Golden West wants to home in on those that pose an imminent threat to Cambodians.

“It’s all about public safety – is a fisherman getting his net caught in it? Is a boat going to hit it? . . . These are the kind of things we look at,” he said. “There are ordinances in the water that will stay there forever, till the end of time. And it’s not going to do anyone any harm. It’s all about how you’re going to use the underwater environment.”

ADDITIONAL REPORTING BY KOAM CHANRASMEY