This is an estuary filled with water at high tide and lying in long melancholy reaches of sand at low tide.
"Cornwall"
G. E. Mitton
There is less to say about the Helford River estuary than any other.
"Cornwall"
G. E. Mitton
He has, therefore, filled up an appointment creating you provincial governor of that part of Britain lying north of the Thames as far as the northern estuary, and bounded on the east by the region of swamps-the land of the Trinobantes, the Iceni, and a portion of the Brigantes-with full power over that country, and answerable only to the propraetor himself.
"Beric the Briton A Story of the Roman Invasion"
G. A. Henty