Simon Worrall explains why a recent discovery on the seabed of the Indian Ocean will revolutionise our understanding of two ancient civilisations.
"The local fishermen believe that there are underwater spirits guarding the wrecks," says Tilman Walterfang, as our boatman picks his way through a maze of coral reefs and submerged rocks.
"Sometimes, they perform prayers on the boats, sacrificing a goat, spreading the blood everywhere, to keep the vessel safe."
I am on a fishing boat in the Gaspar Strait, near Belitung Island, off the south-east coast of Sumatra.
Since time immemorial, this funnel-shaped passage linking the Java Sea and the Indian Ocean has been one of the two main shipping routes. The Malacca Straits is the other, from China to the West.
A British sea captain, shipwrecked here in 1817, called it "the most dangerous area between China and London".
Ten years ago, at a spot known locally as "Black Rock", two men diving for sea cucumbers came across a large pile of sand and coral.
Digging a hole, they reached in and pulled out a barnacle-encrusted bowl. Then another. And another.
They had stumbled on the oldest, most important, marine archaeological discovery ever made in South East Asia, an Arab dhow - or ship - built of teak, coconut wood and hibiscus fibre, packed with a treasure that Indiana Jones could only dream of.
There were 63,000 pieces of gold, silver and ceramics from the fabled Tang dynasty, which flourished between the seventh and 10th centuries.
Among the artefacts was the largest Tang gold cup ever discovered and some of the finest Yue ware - a porcelain that the ancient Chinese likened to snow because of its delicacy.
The artefacts from the find are nearly 1,200 years old
The exceptional quality of the goods has led some scholars to suggest that these were gifts from the Tang Emperor himself.
The bulk of the cargo was more homely, including 40,000 Changsha bowls, named after the Changsha kilns in Hunan Province, where they were produced.
Found packed inside tall, earthenware jars, some experts believe bean sprouts were placed between the bowls as a sort of organic bubble-wrap. These brightly painted tea bowls were the Tang equivalent of plastic food containers.
"It looks like they were approaching Tanjung Pandang, the main town on Belitung Island, when they hit the reef," explains Walterfang, the stocky German treasure hunter who salvaged the wreck.
"They may have come here for water or other supplies. Perhaps there was an emergency. Or even an attack by pirates.
"But we cannot know. It was nearly 1,200 years ago."
Magically, everything was perfectly preserved by a layer of silt. Raised from the seabed more than a millennium later, the gold cups and bronze mirrors, silver boxes and ewers look as fresh as the day they were created.
In 2005, the Singapore government paid more than £20m to acquire the treasure as the centrepiece for a new maritime museum.
But it is not just about bling. The Belitung wreck is a time capsule that has revolutionised our understanding of two ancient civilisations that fill the airwaves today - China and the Middle East.
The serial nature of the cargo - 1,000 miniature funeral urns and 800 identical inkpots - shows that China was mass-producing goods for export several centuries earlier than previously thought.
The Arab dhow, the first of its kind ever found, proves something equally startling - that mariners from the Gulf were trading on a scale, and over distances, unmatched by human beings until Vasco da Gama set sail for India at the end of the 15th Century. Sinbad the Sailor was for real.
One of the Changsha bowls bore a date stamp, "the 16th Day of the seventh Month of the second Year of the Baoli reign", or AD 826. Carbon-14 analysis of some star anise found in the wreck confirmed this as the probable date of the dhow's departure from China.
Most scholars believe it set sail from Canton, or Guangzhou, as it is today, the largest of the five ports servicing the Maritime Silk Route.
China mass-produced export goods centuries earlier than first thought
No-one knows exactly where the dhow was heading when it struck the coral reef.
Its most likely destination was a place familiar to us for other reasons, the Iraqi port of Basra, as it is called today.
In the 9th Century, Basra was one of the wealthiest cities in the world, with a prosperous merchant class hungry for Chinese luxury goods.
Among the most sensational artefacts found in the wreck are three dishes decorated with cobalt from Iran which represent the oldest blue and white ware ever found, setting back by several hundred years the invention of what would become known all over the world simply as "china."
From Our Own Correspondent was broadcast on Saturday, 18 October, 2008 at 1130 BST on BBC Radio 4. Please check the programme schedules for World Service transmission times.