A shipwrecked first-century vessel found off the Spanish coast has been thrilling the archaeologists with the array of information it has been delivering.

With 30 m (100ft) length and a 400 tonnes weight, this Roman ship is the largest found in the Mediterranean, doubling in size the next.

The main good carried by the ship was represented by about 1500 well preserved one meter-high two-handled clay jars of garum, a highly prized fish sauce by healthy Romans as a condiment to a wide variety of dishes and supposedly aphrodisiac.

The sauce is no longer in the amphoras because the eroded ceramic-and-mortar seals were not hermetic to withstand two millennia under water, but traces of fish bone were found inside and these will lead to the sauce's formula.

The ship was probably also transporting ingots of lead, used by Romans for plumbing, and copper, necessary to make bronze, by mixing with tin, for everything from plates to jewelry.

The ship was accidentally found in 2000 when boaters tangled their anchor in a jar.

The ship is also extremely accessible - lying in just 25m (80 feet) of water, and 1.5km (one mile) from the coast of Valencia.

Most shipwrecks are so deeply situated they cannot be examined by scuba divers.

"I am not going to say it was on the beach but almost," said Carles de Juan, from the research team.

Probably, the vessel, 60% of which is now under the mud on the sea floor, sank in a storm while sailing from Cadiz (now in southern Spain) to Rome.

The storm must have been very powerful 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," said De Juan.

When people heard about the discovery in 2000, souvenir hunters scuba divers targeted the site and stole some of the jars, forcing the Valencia government to set a steel thick cage over the wreck to protect it.

After years of fund collecting, a proper exploration of the site began in July 2006.

Marine archaeologists have been conducting the hard work of cataloguing what was on board.

The last Roman ship of large size and good condition was discovered 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.

"No other Roman shipwreck is currently under study in the Mediterranean," he added.

Photo credit: Valencia Regional Government.