The trading ship, previously only seen in an intact state on the side of ancient Greek pottery, was dated back to 400BC.

An ancient Greek trading ship dating back more than 2,400 years has been found intact at the bottom of the Black Sea off the Bulgarian coast, according to researchers, who hailed it as the world’s oldest known shipwreck.

The ship, which is lying on its side with its mast and rudders intact, was dated back to 400BC – a time when the Black Sea was a trading hub filled with Greek colonies.

“A small piece of the vessel has been carbon dated and it is confirmed as the oldest intact shipwreck known to mankind,” the British-led Black Sea Maritime Archaeology Project said in a statement on Tuesday.

This type of ship has previously only been seen in an intact state on the side of ancient Greek pottery such as the Siren Vase held by the British Museum.

The team, which includes British, Bulgarian, Swedish, US and Greek marine archaeologists and maritime scientists, said the vessel was found at a depth of more than 2km.

The water at that depth is oxygen-free, meaning that organic material can be preserved for thousands of years.

“A ship, surviving intact, from the Classical world, lying in over two kilometres of water, is something I would never have believed possible,” said Professor Jon Adams from the University of Southampton in southern England, the project’s main investigator.

“This will change our understanding of shipbuilding and seafaring in the ancient world,” he said.

Helen Farr, a project team member, added: “We have bits of shipwreck which are earlier but this one really looks intact.

“The project as a whole was actually looking at sea level change and the flooding of the Black Sea region … and the shipwrecks are a happy by-product of that,” she told BBC radio.

The Greek vessel is one of more than 60 shipwrecks identified by the project, including Roman ships and a 17th-century Cossack raiding fleet.

In addition to dozens of shipwrecks, they found the remains of an early Bronze Age settlement underwater near the former shore of the Black Sea.

During the three-year project, researchers used specialised remote deep-water camera systems previously used in offshore oil and gas exploration to map the sea floor.

A documentary on the project will open on Tuesday at the British Museum.