The survival of a vessel such as this is extremely rare, and there are no known wrecks of seagoing ships from the 11th to the 14th centuries in English waters. The discovery makes this the earliest English designated wreck site where hull remains can be seen, Bournemouth University writes.

The shipwreck was preserved due to unique environmental factors, according to maritime archaeologists now excavating and analyzing the site.

“Very few 750-year-old ships remain for us to be able to see today, and so we are extremely lucky to have discovered an example as rare as this, and in such good condition,” Tom Cousins, a maritime archaeologist, said in a statement to Bournemouth University. “A combination of low-oxygenated water, sand and stones has helped preserve one side of the ship, and the hull is clearly visible.”

The 13th century ship with its cargo of medieval Purbeck stone is fascinating because it is the earliest English protected wreck site where hull remains are present

Duncan Wilson, Chief Executive of Historic England

The vessel is clinker-built—made from overlapping planks of wood—and was carrying a cargo of Purbeck stone. Quarried on the Isle of Purbeck on the southern coast of England, Purbeck stone is a form of limestone made from densely-packed shells of freshwater snails. The stone is also referred to as Purbeck marble, due to its ability to be highly polished.

The shipwreck is referred to as the ‘Mortar Wreck,’ since much of the cargo contained within the wreck also includes several Purbeck stone mortars, which are large stones used by mills to grind grains into flour.