Almost two dozen new protected areas in the UK's seas have been announced to help preserve habitats and wildlife.
The 23 new marine conservation zones designated by the Government include cold water coral reefs, sea fan "forests", canyons and sandbanks, and provide homes and food for wildlife ranging from seabirds to peacock worms, as well as commercial fish stocks.
They include places such as Land's End, with its rugged coastline and waters visited by whales, dolphins, leatherback turtles and basking sharks, and the Cromer shoal chalk beds in the North Sea - thought to be the largest chalk reefs in Europe.
The second tranche of protected areas covering 4,155 square miles, and bringing the total so far to 50 marine conservation zones, was welcomed by conservationists as a step to creating a "blue belt" in the UK's seas, providing protection from harmful activities such as over-fishing.
But they warned there was more to be done to ensure the protected areas were properly managed and to achieve the "much-needed ambitious and comprehensive third and final tranche" of conservation zones.
The Government has designated all 23 of the proposed marine conservation zones it consulted on last year.
It has also said it will consult on establishing new marine "special protection areas (SPAs) to protect areas used by seabirds, and new "special areas of conservation" for harbour porpoises in waters around England, Wales and Northern Ireland.
It will consult on the third tranche of marine conservation zones in 2017.
Marine Environment Minister George Eustice said: "As an island nation, the UK is surrounded by some of the richest and most diverse sea life in the world - from the bright pink sea-fan coral colonies off the south-west coast, to the great chalk reef stretches in the east.
"It's vital that we protect our marine environment to ensure our seas remain healthy, our fishing industry remains prosperous and future generations can enjoy our beautiful beaches, coastline and waters.
"By designating these new marine conservation zones and creating a blue belt of protected areas around the country, we can better protect our environment through careful marine management in years to come."
Joan Edwards, head of living seas at the Wildlife Trusts, welcomed the move.
She said: "This second step towards the completion of a 'blue belt' in UK seas is crucial in turning the tide on the state of our seas, but there's still work to be done.
"We look forward to working with the Government and stakeholders to ensure these 50 marine conservation zones are properly managed and to achieve the much-needed ambitious and comprehensive third and final tranche.
"This will be the start of turning our over-fished, over-exploited and currently under-protected waters back into a healthy and sustainable environment."
Natural England chairman Andrew Sells said: "This is a fantastic outcome for the marine environment and brings us a step closer to achieving the ambition of a 'blue belt' - a network of marine areas protecting wildlife surrounding the UK."
The 23 marine conservation zones are:
North Sea: Fulmar, Farnes East, Coquet to St Mary's, Runswick Bay, Holderness Inshore, Cromer Shoal Chalk Beds.
South East: The Swale Estuary, Dover to Deal, Dover to Folkestone, Offshore Brighton, Offshore Overfalls, Utopia, The Needles.
South West: Western Channel, Mounts Bay, Runnel Stone, Newquay and The Gannel, Hartland Point to Tintagel, Bideford to Foreland Point, North-West of Jones Bank, Greater Haig Fras.
Irish Sea: West of Walney, Allonby Bay.