The government created 15 new Marine Protected Areas, designed to protect important habitats and species.
The sites will bring protection to habitats including reefs, sea caves and sandbanks.
“Our seas are home to some of the most diverse species and habitats in the world and they need just as much protection as our land,” Marine Environment Minister Richard Benyon said.
“Today is a major step forward in helping us to achieve clean, healthy and vibrant seas where marine life can thrive.”
The sites will bring protection to habitats including reefs, sea caves and sandbanks, the Department for Environment, Food and Rural Affairs said.
Sandbanks act as nursery grounds for many commercial fish species such as plaice and sole while also supporting sand eel communities that are a food source for seabirds and mammals such as seals, it said.
Reefs support sponges, sea squirts and corals that provide shelter for crabs, lobsters and fish such as the multi-coloured cuckoo wrasse. Birds will also benefit with sites selected for the conservation of the red-throated diver and common scoter, the ministry said.
Fishing, dredging and other activities, including wind turbines, will be banned or restricted on the 15 sites, according to reports.
The government has submitted the sites to the European Commission to be included within the European Natura 2000 network of protected areas.