By Alastair Lawson
BBC News, Bangladesh
The sunken valuables of some of South Asia's largest rivers are being retrieved by a daring new breed of amateur diver in Bangladesh.
The divers work in dangerous conditions
Using a pipe connected to a rudimentary oxygen compressor, the divers say they can go as low as 200ft in some of the world's most fast-flowing rivers.
It's a kind of low-tech scuba diving.
The divers collect valuables and artefacts from vessels that have sunk in strong currents in wet and windy weather.
Every year ferries sink in Bangladesh, especially during the monsoon season.
Sometimes the divers - who earn around $6 a day - are called upon to recover the bodies of people who have been killed in ferry disasters.
They ply their trade in rivers such as the Buriganga, the Padma [in India known as the Ganges] and the Meghna.
Mr Hossain has had no formal training in diving
The divers say that they can remain underwater for up to one and half hours. They communicate with each other using hand signals, even though visibility in the murky waters is often less than three feet.
Known locally as "khoji" or "those who search for something", the divers use a pipe connected to a compressor which is normally used for blowing up tyres.
They go out into the middle of the river on a boat, tie themselves to a rope and dive in.
The idea is that if they get into any kind of trouble, they pull on the rope to indicate that there is an emergency.
Muhammad Jahangir Hossain is one such diver. He has no formal training and was taught by his brother how to dive.
"I began by scooping up sand from the river bed which was used for construction purposes," he said.
"On this part of the Meghna quite a few boats capsize and later I was diving down to a big vessel which capsized while carrying a huge amount of wheat.
"I recovered the sacks of wheat, dried them under the sun and sold them in the market."
In the past when a cargo boat capsized, professional divers arrived to recover parts of the ship such as propellers, turbines and other engine parts.
"It was then when I decided to buy a compressor and enter the market," Mr Hossain said.
He says that his friends know how deep he is by the length of air-hose that is used.
"Without oxygen I can dive 45 feet (13.7m)," he said.
His biggest job so far was diving down to a cargo boat.
It took a week for Mr Hossain and 12 other "compressor divers" to cut up the vessel and recover it in pieces.
"We ran wires under her, and with the help of a crane we were able to bring her back to the surface. We made a cool 250,000 Taka ($3,571) for the job," he said.
Mr Hossain says that he has no plans at present to open a school for "compressor divers" but such is the money made by these latter-day treasure hunters perhaps that will only be a question of time.