Archaeologists have begun excavating the remains of a rare shipwreck on Tankerton Beach near Whitstable.

The wreck was found on inter-tidal mudflats on Tankerton beach last April, by members of local archaeology group Timescapes who were looking for demolished Second World War pillboxes.

Following a survey of the remains, experts estimate the vessel dates back to the late 16th or early 17th century, and was a carvel-built merchant ship of up to 200 tonnes.

Archaeologists hope their excavation will reveal more information about the ship and what it was used for – including sailors' personal effects, and cargo.

Maritime archaeologist Mark Dunkley said: "We're here excavating for the next three days the very bottom remains of a very rare and significant 16th century trading ship.

"It was probably ocean-going – we know that because we've found the remains of a galley on board, as well as remains of the crew's artefacts and cooking equipment. But the most significant thing about what it's doing here is its relationship to Tankerton.

"Tankerton, in the same period of the 16th and 17th century, was a net exporter of a locally-produced good called copperas.

"So we can use this to understand that perhaps this ship here was transporting barrels of copperas to the rest of England. Samples of the mud from the very bottom show sediment from other places, showing where it may have traded.

"It shows the role Whitstable and Tankerton could have played in the expansion of the British Empire."

Copperas, also known as green vitriol – hydrated ferrous sulphate – was largely used in the textile industry as a dye fixative and in the manufacture of ink.

A well-known copperas works was in operation in nearby Whitstable from 1565.

The Department for Digital, Culture, Media and Sport has now scheduled the Tankerton wreck on the advice of Historic England, giving it protection.

Historic England has commissioned Wessex Archaeology, with the help of volunteers from Timescapes, to survey the exposed remains which measure just over 12m long by 5m wide.

The wreck has been miraculously preserved by the layer of London clay in which it sits.

But its location also poses a problem to archaeologists. As it is only exposed when the tide is low, excavators are only able to work on it at certain times of the day.

Each time they recommence work, they must use buckets and a pump system to dredge seawater out of the excavated area.

Two trenches that have already been excavated have revealed the presence of well-preserved hull timbers from the keel up to the turn of the bilge, where the bottom of the ship curves to meet the vertical sides.

Dendrochronological sampling, which uses tree rings, has revealed that one oak plank is of southern British woodland origin with a felling date of AD1531. Three other oak samples were tentatively dated to the 16th century, with elm, larch and beech timbers.

The Tankerton wreck has been given protection because it is the only known surviving medieval shipwreck in south east England. It gives evidence of Tudor and early Stuart shipbuilding techniques, as well as the late medieval copperas industry along the north Kent coast.

Another ship has also been uncovered at Camber Sands, near Rye in East Sussex. This discovery has also been given protection.

Duncan Wilson, chief executive of Historic England, said: “These two very different ships are equally fascinating and will shed light on our maritime past. Many of the ships that Historic England protects are accessible only to divers but when the sands shift and the tide is right, visitors to these beaches in Kent and Sussex can catch a glimpse of these incredible wrecks.

"I’m delighted that volunteers are so involved in discovery, which is one of the great gifts of the historic environment."

Work began at the Tankerton site on Friday, and will likely continue until Thursday.