Mike Dilger goes underwater at Norfolk's chalk reef
Naturalist Mike Dilger joins an underwater diving expedition to survey Norfolk's coastal chalk reef in a new BBC TV documentary.
This rare habitat is teeming with marine life including purple sea slugs, orange anemones, sea squirts, and small crabs that camouflage themselves by sticking seaweed to their shells.
The water is so clear it is hard to believe this is not the Red Sea, yet it is a stone's throw from the windswept beaches of Norfolk.
Britain's Great Reef will be broadcast on Monday, 10 October at 19:30 BST on BBC One East and available afterwards on BBC iPlayer.