A 200-year-old Chinese mansion in Bangkok's heart isn't an obvious place for a scuba school, but in a city relentlessly demolishing its architectural heritage the business is helping preserve the historic home.
Diving instructor Poosak Posayachinda's family has owned the traditional teak-walled So Heng Tai for eight generations, and now it lives on thanks largely to his decision to convert it into a scuba academy.
The survival of the building, originally built as a home and office for the family's business in trading birds nests, is a rare success story in a city that harbors little sentiment - or legal protections - for historic architectural gems.
"It's because people want to make more money - that's the bottom line," Bangkok-based American architect Bill Bensley says.
The city's breakneck reinvention over recent years has seen gleaming malls and flashy condos go up and buildings like the art deco Scala cinema and the 1920s British embassy come down.
Thai law only protects properties over 100 years old, and political enthusiasm for safeguarding old architecture at the expense of profitable development is limited.
For families with historic properties, maintenance costs can be a huge liability, says historian and archaeologist Phacha Phanomvan. "We don't have a lottery fund or trust body that comes in to save heritage."
So in 2004 Poosak installed a four-meter-deep pool in the So Heng Tai courtyard, subsequently teaching more than 6,000 students.
The diving school has helped pay the bills for the property's upkeep, but maintenance is a struggle.
"On a rainy day you find lots of water spots," Poosak says. "Sooner or later we will have to do the whole roof again and that's a lot of money."
While the culture ministry keeps a national heritage database many properties are not registered and fall through the cracks.
"For individual owners without state assistance it's better for them to sell the property," Phacha says.
Adding to the challenge is a growing collectors' market for teak from Thai wooden houses. Some are dismantled and reassembled to become boutique hotels elsewhere.
Photographer Ben Davies spent five years documenting neighborhoods for his book Vanishing Bangkok - an experience that left him despondent.
"Something like 30-40 percent of the buildings and communities I photographed have either disappeared or changed virtually beyond recognition," he says.
And in the rush to develop, Davies says it is unclear how much of Bangkok's heritage will remain in a decade. "I have a horrible feeling that one day Bangkok will be, outside of its temples and few palaces, like any other megacity around Asia."
But there are glimmers of hope.
In recent years a prominent Sino-Thai business family renovated dilapidated 1850s Chinese-style warehouses, turning them into the Lhong 1919 "riverside heritage destination."
It now houses a shrine and has become a space for exhibitions, concerts, pop-ups, cafes and food vans.
Back at So Heng Thai, Poosak takes his students through their paces.
Channeling the attitude of his ancestors - who arrived in Thailand with "one pillow and one mattress" - he's determined to save his family home.
"If someone comes to give me an offer, the answer is no, simple as that, no matter how much it is," he says.
So Heng Tai was opened up by Poosak Posayachinda to learner divers or Bangkok denizens looking for a cuppa or relics from the past.
