It isn't easy getting to Hailing Island. As ever in China, there is the language barrier. I have been told to head for Yanjiang, a provincial city about three hours south-west of Guangzhou, or Can ton, as it used to be. But the receptionist at my hotel hears the name of the city as Zhangjiang. Finally, after much poring over maps, we get the right place.
But how to get there? My intention is to go by bus. The receptionist insists this will be too complicated - and too dangerous. I might be robbed. So, after much further discussion, I negotiate with a taxi driver to drive me for the princely sum of 1,400 yuan - nearly £100. Welcome to the new China.
It is more than twenty years since I have been here. In 1984, I took a job as a so-called "foreign expert" - very foreign, not very expert - teaching English at a university in Manchuria. It was less than a decade after the Cultural Revolution. People still dressed in Mao suits and caps and got around on old-fashioned Phoenix bicycles or "the number 11 bus", a colloquialism meaning your own two feet. The only shops were Soviet-style department stores.
It is a be wildering experience to arrive back in China two decades later. Motorbikes have replaced the rivers of bicycles that used to flow through the streets. There are skyscrapers, Mercedes Benz cars and neon lights, and hookers in every hotel. Yet as we leave Guangzhou and head into the interior, it is much as I remember it. Hibiscus bushes line the middle of the highway. Peasants in bamboo hats pull wooden handcarts beside rice paddies and fishponds. A bare-chested man with skin the colour of teak holds three water buffaloes on a web of chains on the grass at the side of the road.
It takes more than three hours to reach Hailing Island. Finally, we cross a causeway and a choppy, grey sea appears. Billboards decorated with leaping dolphins and girls in old-fashioned bathing suits appear at the side of the road.
Hailing Island is a popular holiday resort (think Seaton by the South China Sea). On the island's main drag there are numerous restaurants with pink plastic furniture and exotic fish in tanks. Roadside stalls sell beach umbrellas, suncream and garish towels. Holidaymakers, many of them from Taiwan, pad along in flip-flops, eating ice creams.
I am not here for a holiday, though. I have come to meet a man called Zhang Wei, head of China's marine archaeology unit. An energetic man of 52 with a winning smile and a mop of black hair, he drives an Audi and dresses in smart western clothes. Dangling from a silver chain under his pink cotton shirt is a chunk of jade worth more than £1,000. His cellphone rings incessantly.
"We estimate that there are 2,000 ancient shipwrecks in the territorial waters of China," he says, as we sit drinking "Kungfu" tea from thimble-sized cups at the marine archaeology unit's base, which doubles as a hotel. In a classroom below us, a group of students, including two from Kenya, pore over barometric tables. Through the window, we can see brightly painted fishing boats bobbing on the waves. "We have identified more than a hundred sites off the coast of Guangdong and Fujian alone."
Until recently, the Chinese paid little attention to the treasures buried beneath their territorial waters. There were more than enough on land. But the 1986 Christie's auction of Ming porcelain salvaged by the buccaneering British treasure hunter Michael Hatcher, which raised £10m, changed that. "The Chinese government decided to create its own organisation to salvage marine artefacts," explains Zhang, "to prevent treasure-hunters like Hatcher from exploiting them."
Paradoxically, Zhang grew up far from the sea, in Beijing (his first sight of it came during his honeymoon, at the age of 26), and originally trained as a land archaeologist. In 1987, however, after studying in Holland and the US, he became China's first marine archaeologist. "Marine archaeology was a blank page at that time," he recalls. "There was no equipment, no survey maps, nothing. I wanted to make history."
His chance came in 1997 when he and his team, working with a group of British divers, located a 12th-century ship loaded with ceramics off the Pearl River estuary. Named the Nanhai 1 (Nanhai is the Mandarin term for South China Sea) and dubbed the "Titanic of China" by the local media, it was a Song Dynasty (960-1279) merchant ship that sank around 840 years ago on its way to the Middle East. On board was a trove of between 40,000 and 60,000 artefacts, mostly ceramics to be sold at Arabian markets.
Just before Christmas last year, in the first operation of its kind in the world, the ship, with its cargo still on board, was hoisted from the seabed in a giant steel box and towed to the shore, where it will be exhibited at a new maritime museum.
Foreign treasure-hunters such as Hatcher are forbidden in China, but the country's rich underwater heritage attracts local gangs, mostly ex-fishermen, known as dao bao zhe or literally "loot treasure people". China's new wealth has fired a hunger for antiques. Private ceramics collections are booming. For the nouveau riche businessman, a Ming vase or piece of Song celadon lends an aura of culture and refinement.
"We call these things sea-looted porcelain," explains Zhang. "You can buy them in antique markets in Beijing or Shanghai. The police can't prove that they are looted because they are in private hands. Though last year in Fujian, some black-market dealers were caught and jailed."
Looted artefacts are now even used as hung bao - literally "red envelope", Chinese slang for a bribe, after the custom of giving a red envelope containing money to newly-weds or children. Ten important sites have already been looted. And, with three million square kilometres of ocean, it is almost impossible to eradicate the practice. "Da hai lao zhen," says Zhang Wei, quoting an old Chinese proverb: "It's like looking for a needle in the sea."