Dozens of divers, equipped only with goggles and plastic oxygen hoses, have plunged into the fast-flowing waters in search of the long-lost Dhammazedi bell, in a spectacle that has generated scepticism but also attracted lines of spectators along the riverbank since the search began earlier this month.
The group is the latest in a series of treasure hunters eager to try to raise the near-mythical giant bell, which is said to have sunk without trace after being stolen from Rangoon's revered Shwedagon Pagoda by a Portuguese mercenary in the 1600s.
It was reputedly loaded onto a boat which sank under the weight.
"After asking permission from all noble persons and saints, we definitively declare that we have found the Dhammazedi bell," said a statement from lead organiser San Lin.
He has not so far provided any proof.
The search has attracted criticism among Myanmar historians, some of whom question the very existence of the bell.
Organisers have rejected hi-tech equipment in favour of spiritual practices, performing rituals on their boat in the centre of the swollen river to appease dragon spirits said to be protecting the bell.
"It can be found if we organise and research systematically. But it cannot be found like this -- following astrologers' advice and inviting Nats (spirits), dragons and galouns (mythical birds)," Chit San Win, of the Myanmar Historical Commission, told AFP.
San Lin, who says he originally saw the bell on the riverbed during a 1998 salvage attempt and has received funding from a local private bank, vowed to lift the bell from the water within days.
- As heavy as a Boeing 777 -
Fashioned mainly out of bronze, the Dhammazedi bronze bell is said to have weighed 294 tonnes -- about the same as the maximum take-off weight of a Boeing 777.
Historians believe it was donated to the Shwedagon pagoda in 1484 by the Mon King Dhammazedi, who ruled the southern part of Myanmar at the time.
It was then believed to have been stolen from the revered temple by Portuguese merchant Filipe De Brito e Nicote -- known locally as Nga Zinka -- who had seized control of an area south of Rangoon and wanted to melt down the bronze to make cannons.
While no definitive proof has yet been uncovered of the bell's existence, the search operation has garnered a following of hopeful supporters.
"I came here to encourage the salvage operation -- I really want them to get it," said housewife Aye Aye Mar, who had travelled for hours from her home to witness the salvage attempt.
But others are more cynical, with social media buzzing with posts mocking some local media reports that appeared to present as fact the involvement of a dragon in the salvage.
"Can I get the phone number of the dragon?" asked one of many similar posts.