A £2.6m appeal has been launched to help the National Trust buy a "magical" stretch of coastline.
The trust wants to buy Bantham beach and the Avon estuary in south Devon.
A family-owned estate including the beach, estuary, about 20 cottages in Bantham village and about 750 acres of land is on the market for £11.5m.
The trust said it plans to maintain access for visitors to the beach and conserve the landscape of the wooded river valley.
But it has decided not to bid for the cottages, saying its core purpose was not to be a social landlord.
The beach has panoramic views over Bigbury Bay and is described as the best surfing beach in south Devon.
The trust fears access to the beach could be reduced and the coastline could be at risk of inappropriate development if another buyer snaps it up.
It has already been able to commit £4.6m to the purchase from its Neptune campaign to protect coastal areas, but urgently needs to raise another £2.6m to buy the beach and estuary and pay initial management and conservation costs.
If successful, it would be the National Trust's most expensive coastal purchase.
Mark Harold, National Trust director for the South West, said: "This is a magical place, a true jewel on the South West coast.
"If we don't raise the money then the future of Bantham beach and the Avon estuary is uncertain and this stretch of coastline might one day be disrupted by inappropriate management or development."
The proposed purchase would add to the 742 miles of coastline around England, Wales and Northern Ireland, including beaches, cliffs, islands, sand dunes and estuaries, which is cared for by the National Trust.