One morning in 2019 Lieutenant Nguyen Nhat Phong leaves his bowl of instant noodles unfinished and rushes to pack his equipment and suit after receiving orders to search for a shotgun a suspect had reportedly thrown into a canal four hours earlier.

At 7 a.m. Phong, 27, and seven others from the search-rescue team at the Ho Chi Minh City Fire Prevention and Fighting and Rescue Police Division (PC07) squeeze themselves into diving suits, strap a 20-kg oxygen cylinder on their backs and stand on the bank of the Lang Le Canal in An Phu Dong Ward in District 12.

Phong and the others dive into the blackish water filled with garbage and the occasional dead rat, searching for a potential murder weapon along a 1.5-km stretch of bottom.

In some parts, the water is six meters deep, in others the mud is knee-deep and Phong cannot even move his feet.

After three hours in the murky, stinky water, the team ends up finding just animal bones, shards of glass and some rusted iron bars.

They then wait for the canal to be as calm as it could before making a second attempt.

They change their strategy this time: The eight men line up in a row and scour the bottom inch by inch, gradually moving forward.

By noon, as hope begins to run out, Phong touches something that feels like a tree trunk connected to a piece of metal. With his instinct telling him he had struck pay dirt, he surges to the surface. When he sees clearly he is holding a shotgun stock in his hand, he shouts with joy.

"I was so happy that I opened my mouth to scream and swallowed the dirty water," he recalls.

Continuing the search, the team then finds the gun barrel and a plastic bag with two cartridges inside.

Nguyen Nhat Phong hands over parts of the shotgun he and his team found in the bed of
the Lang Le Canal in HCMC's District 12, 2019. Photo by the HCMC Fire Prevention and
Fighting and Rescue Police Division.

The gun had been used by Nguyen Lam Ngoc Hung, 43, to shoot dead Le Tan Vu, 28, early in the morning on October 17, 2019.

Hung told the police he had been high on drugs while partying with friends at home, and "accidentally" pulled the trigger and put a bullet through Vu’s head.

Hung disassembled the gun and threw the parts into the canal. His wife told the police where he threw the gun. Two weeks after the killing, Hung turned himself in.

Three months before Phong and his team found the shotgun, Corp Nguyen Hong Van and 10 other officers had searched a 100-meter section of the Lo Gom Canal in Ward 7, District 6, for a knife a man was suspected of using to stab another to death.

After three hours under water that was "as black as oil," Van was over the moon when he found the knife that was the length of a human hand.

Before he found it, his colleagues had had their hands cut by shards of glass.

"In those blackish canals, we are as good as blind and have to use our hands to feel everything under the water," he says.

Hand injuries "happen all the time" to him and others, he says.

But he considers himself lucky since several others in his team had to receive treatment for possible HIV infection from needles.

The search-rescue team has 33 men whose main task, besides searching for and rescuing victims at accident sites, is looking for evidence in waterways.

New recruits must spend months mastering diving skills before starting to learn on the job, Colonel Dao Quoc Trung, the head of the team, says.

Captain Nguyen Truong Nam says he can never forget an incident five years ago when he almost died after the valve of his oxygen tank broke more than 20 meters under water while he was trying to salvage a boat sunk by illegal sand miners in a river.

He could not untie the rope connecting him with his teammates or inform the others about his deadly predicament.

But after a struggle, he managed to untie the rope and rise to the surface.

"I am lucky to be still alive," he says.

His most recent mission was also a memorable one, he says. He had to search for sections of an underwater cable system costing VND2 billion ($86,190) in Nha Rong Wharf in District 4 earlier this year.

On the day the wharf resumed operation after the Lunar New Year break an employee turned on a circuit breaker to provide power for ships docked at the wharf, but there was no signal.

When the staff opened the covers of five ditches to check the cable system, they found nothing unusual. Three weeks of investigation brought them no closer to an answer.

Nam and his team were then brought in to dive into the Saigon River to check the entire cable system.

One morning in February Nam entered the river through one of the ditches. Soon he discovered many thin rubber pieces placed just next to the power cable line. He realized that thieves had cut the cable, stole some sections and replaced them with those rubber pieces.

That explained why the wharf staff did not detect anything when checking the camera footage. The thieves had left the cable sections under the five trenches untouched so that when someone checked by looking down the trenches, they would not notice anything amiss.

In all, more than 100 meters of power cable had been stolen.

In September a team of six was sent to search for a safe weighing more than 40 kilograms in the Dia Canal in Nha Be District.

Thieves had broken it open to take the cash and jewelry inside and then carried it to the Phuoc Long Bridge to toss it into the water below.

As the water was flowing strongly, the divers had to carry tens of kilograms of ballast to remain steady. After three hours of searching Phong felt something "hard as rock."

He felt the object and found four knobs on its surface, and decided to tie it to a rope signed for the others to pull it up.

Divers of the PC07's search-rescue team carry a safe out of the Dia Canal
in Nha Be District. Photo by VnExpress/Dinh Van.

A gruesome task the team has is to search for bodies in canals and rivers.

Trung, head of the team, can hardly forget the first time he pulled a body out of the water.

He was 20 then and the moment he felt the hair on the head of a dead woman at the foot of Kieu Bridge in Phu Nhuan District, he panicked, dropped the snorkel and swallowed a lot of water. He had to be sent to a hospital and have his stomach pumped.

"For those who are new to this job, throwing up and skipping meals after retrieving bodies is par for the course," he says.

Colonel Huynh Quang Tam, head of the PC07, says every year the unit collaborates with crime investigation agencies on around 40 cases and the success rate is always around 90 percent.

"Evidence plays a crucial role in proving a suspect guilty, and so, however dangerous and difficult it is, we always try our best to find it.

"The desire to find submerged evidence at any cost is the magnet that keeps attracting officers to the hard job."