For three years, an international team of scientists surveyed the floor of the Black Sea, off the coast of Bulgaria. Now, radiocarbon tests have confirmed that the remains of an ancient ship discovered late last year date from 400BC, officially making it the world's oldest known intact shipwreck.

The ship was a Greek trading vessel, of a type that was previously only known from depictions on the sides of ancient pieces of pottery – these include the Siren Vase, which is on display at the British Museum, and is pictured below.

Located under 2 km (1.2 miles) of water, the shipwreck remained intact thanks to the fact that water at such a depth is anoxic (oxygen-free), allowing organic material such as wood to stay preserved for thousands of years. The wreck was surveyed and mapped utilizing two remotely-operated underwater vehicles, one of which retrieved a small sample that was used for the radiocarbon dating.

The discovery was part of the larger Black Sea Maritime Archaeology Project (Black Sea MAP), which is led by the UK's University of Southampton, and includes scientists from the Bulgarian Academy of Sciences and Bulgaria's Center of Underwater Archaeology. Since its start in 2015, the effort surveyed over 2,000 sq km (722 sq mi) of the seabed, discovering more than 60 shipwrecks including a 17th century Cossack raiding fleet and Roman trading vessels carrying amphorae.

The latest finding, however, is certainly the most significant.

"A ship, surviving intact, from the Classical world, lying in over 2 km of water, is something I would never have believed possible," says Southampton's Prof. Jon Adams, the project's principal investigator. "This will change our understanding of shipbuilding and seafaring in the ancient world."

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