The valuable cargo was probably being shipped from Cadiz to Rome

Thirty metres (100ft) long and holding 400 tonnes, it is the largest Roman ship found in the Mediterranean.

Chief amongst the goods the ship was carrying were hundreds of jars of garum - a fish sauce which was a favourite condiment for rich Romans.

It was accidentally discovered in 2000 by sailors whose anchor snagged a jar.

The ship is in great condition and extremely accessible - lying in just 25m of water, and 1.5km (one mile) from the coast of Valencia.

"I am not going to say it was on the beach but almost," said Carles de Juan, who is co-director of the wreck's research team and was among the first divers to examine it.

We knew it was an important find, but had no real idea until now. It is an exceptional find Project co-director Carles de Juan

It is believed that the vessel, 60% of which is now buried in mud on the sea floor, went down in a storm while sailing from Cadiz in southern Spain to Rome.

Mr de Juan said that the storm must have been of immense strength to drive such a vessel so close to shore.

"The crew did not care about the cargo or money or anything. They headed for land to save their lives," he said.

First proper study

Once news of the ship's discovery was announced in 2000, souvenir hunters targeted it, forcing the Spanish authorities to erect a steel cage around the wreck to protect it.

After years of arranging funds, expertise and equipment, a proper exploration of the site began in July of this year.

Since then, marine archaeologists have been conducting the painstaking work of cataloguing what was on board.

"We knew it was an important find, but had no real idea until now," Mr de Juan said in an interview with the Associated Press after he and project co-director Franca Ciberchinni of Italy's University of Pisa presented their first academic report on the site.

"It is an exceptional find," Mr de Juan added.

An estimated 1,500 two-handled amphorae, or clay jars, were on board.

Aphrodisiac

The researchers established from remains of fish bones inside that the metre-high jars, which lay undisturbed but with eroded seals, were carrying garum.

The highly-prized delicacy was served to wealthy Romans as an accompaniment to a wide variety of dishes and was believed to be an aphrodisiac.

It is thought that the ship was also carrying ingots of lead to be used in plumbing and copper, which could be mixed with tin to make bronze artefacts.

The last time a Roman ship of similar size and good condition was discovered was off Corsica in 1985.

"For archaeologists, a sunken ship is a historic document that tells us about ancient history and how its economy worked," Javier Nieto, director of the Centre for Underwater Archaeology of Catalonia, said of the find.

"This ship will contribute a lot," he added.