Described as a tombolo, research has shown that it is actually a barrier beach which “rolled” landwards. Eventually joining the Isle of the Portland and the mainland giving the appearance of a tombolo.
Against the cliffs of the Isle of Portland on the eastern edge of the beach at the village of Chiswell, the beach curves sharply forming the Chesil cove, which protects the low-lying village from flooding. Westwards the shingle forms a straight line along the coast, enclosing a shallow tidal lagoon called the Fleet.
The Fleet is home to many wading birds, and at Abbotsbury there is a swannery. The only managed colony of nesting Mute Swans in the world. Numbering over 600 swans with approximately 150 breeding pairs. Records of the swannery exist as far back as 1393 AD.
Stretching 10 miles ( or 18 sources differ) long and 40 feet high, the shingle that forms the beach varies form pea-sized at the north-west end to orange-sized at the south-east end. It's said that smugglers who landed on the beach at night, could tell exactly where they were on the beach by the size of the shingle.
During the Second World War the area was chosen, due to the low population density to be one of the testing grounds for the bouncing bomb and machine gun training for Operation Chastise. Many defences were also constructed around the area. Such as anti-tank blocks near Abbotsbury, and on the western side of the beach Admiralty scaffolding, flame fougasse instalations and minefields further inland.