Over centuries the treacherous Goodwin Sands off Kent – known as the great “ship swallower” – has entombed more than 2,000 shipwrecks, dozens of second world war aircraft and is the final resting place of thousands. Shakespeare described it as “a very dangerous flat, and fatal”.

In 1703, five vessels were sucked into its shifting sands during a storm, including the English warship HMS Northumberland, which only now is yielding its well-preserved secrets.

Campaigners fear this unique area is now at risk from destructive dredging for building sand and aggregate. They are appealing to the crown estate, which owns the seabed, and calling on King Charles for support, to protect an area rich in maritime and cultural heritage.

Writing to Charles, as a “committed conservationist, head of the armed forces and as a beneficiary of the crown estate’s commercial activities”, the Goodwin Sands Conservation Trust has asked him to encourage the crown estate to remove the sands from its list of potential marine aggregate extraction sites. The king’s public duties are paid by the sovereign grant, calculated on a percentage of crown estate profits.

“Does he know where this money is coming from? It’s coming from licences to develop the seabed without proper protections for what they are going to find,” said Joanna Thomson, the trust’s chair.

A response from a palace aide referred it to the crown estate. “We made clear in our letter it was because we had got nowhere with the crown estate that we were contacting the king, so the reply was rather frustrating,” said Thomson.

The Goodwin Sands seabed is littered with history. As well as shipwrecks, second world war allied and axis planes crashed in the area long seen as a profitable source of marine aggregate, the trust said.

A licence to extract 2.5m tonnes was approved in 2018 for a Dover Harbour Board development, although it was eventually sourced from elsewhere. Marine aggregate extraction licences are granted by the Marine Management Organisation (MMO), but it is the crown estate that decides what development occurs on the seabed, said campaigners. They are “disappointed” at its “flat refusal” to guarantee no dredging of the 10-mile sandbank, which has had marine protected area (MPA) status since 2019, and acts as a sea defence to the unstable coastline.

Historian and TV presenter Dan Snow, who has dived on the Goodwins, said: “There are some extraordinary wrecks down there. We are obviously all very worried and sad to think it could be just mined and a lot of that would be destroyed.”

Snow described it has a “magical subsea landscape”.

“Every period of our history over the last 2,000 years has left a rich legacy there, which is unusual, probably unique,” he added.

The crown estate said in a statement: “There are currently no plans for aggregate licences in the Goodwin Sands area. However, we are unable to provide blanket, permanent exemptions for any part of the seabed from this or other sectors, unless predicated by an organisation with regulatory or other relevant responsibility, or by a national designation such as a highly protected marine area (HPMA).”

While the MMO grants marine licences for dredging, the crown estate, as landowner, must license or lease the seabed and can decline to do so and not leave the matter solely to MMO marine licensing, according to Michael Williams, visiting professor of law at Plymouth University and an expert on law relating to foreshore, seabed and underwater cultural heritage.

“The crown estate can’t treat it as though the Goodwins have a blanket designation, but what they can do is have a policy. You can say this is a highly sensitive archeological area and therefore we will tend not to grant applications unless there’s exceptional circumstances. And that’s what public bodies do for culturally sensitive areas all the time.”

He added: “The high archaeological potential of the Goodwin Sands is, or should be, a material consideration for the crown estate, even though there is no specific designation of the area in general.” Under the UK marine policy statement’s national policy, just because something is not specifically designated does not mean it is not of importance and the crown estate should take note of that policy, he said.

The MMO is currently consulting on banning bottom trawling in certain areas, including the Goodwin marine conservation area, yet aggregate extraction is far more destructive, said Thomson.

Another potential threat looms. National Grid wants to build an electricity converter station on Minster Marshes near the coast at Sandwich, with a cable running across Sandwich Bay, the site of many shipwrecks and just a few miles away from the Goodwins, “They need half a million tonnes of sand and there are fears they will wish to take it from the Goodwins,” said Thomson.

Wessex Archaeology has identified the Goodwin Sands as holding probably the highest density of maritime heritage in UK waters, said Thomson. “If a dredger went through the remains, they would be completely destroyed. Aircraft could have crew in them, so disturbing final resting places. It’s so hypocritical. Every year we have Remembrance Day at beautiful cemeteries on land, yet there’s the crown estate potentially allowing dredgers to run riot through graves, where people are buried and have drowned. It’s a psychological loss to the nation, and an emotional loss. We wouldn’t allow that to happen on land,” said Thomson.