By Richard Black
Environment correspondent, BBC News
Over-fishing means species such as cod remain in peril
The government has published its long awaited Marine Bill, promising better protection for wildlife including a new network of nature reserves at sea.
The bill also pledges better management of inshore fisheries and measures to speed up the approvals process for offshore windfarms by about a year.
In England, it will open a new right of public access to coastal lands.
Environmental groups say UK seas are "in crisis", and need more protection than the government is offering.
The draft bill creates a new agency, the Marine Management Organisation (MMO), to enforce environmental laws and regulate development at sea.
Launching the bill, Environment Secretary Hilary Benn suggested there was a need to look after the seas and the wildlife they contain as a range of environmental threats looms.
"Our seas are already showing the effects of climate change," he said, "and with increasing use of the sea by many competing interests, we must make sure that the marine environment can cope with changing conditions.
"We have a duty to look after our seas for future generations."
Having been promised the bill in the 2005 Queen's Speech, environmental groups are generally glad that it has finally arrived but have reservations over likely extent of protected areas.
"This is a huge leap forward from the current situation where only 0.001% of UK seas are offered high levels of protection from damaging activities," said Sally Bailey, northeast Atlantic marine manager for the conservation group WWF UK.
"There is a considerable body of work suggesting that a network of marine protected areas should cover from 20-30% of waters, with some work even suggesting as much as 40%."
Currently, UK waters have just three "highly protected" marine reserves, at Strangford Lough in Northern Ireland, Skomer in Pembrokeshire, and Lundy Island off the North Devon coast.
The new areas, to be known as "marine conservation zones", will not automatically have complete protection.
Instead, the government says that "varying levels of protection will be given to individual sites, from restricting certain activities, to 'Highly Protected Marine Reserves' where no damaging activities are allowed".
The final say on which areas are selected and how much protection they receive will rest with ministers.
The English coast will see a new "right to roam" established, with few areas such as railway lines and MOD sites off limits.
"Access to the coastline is a highly prized public asset, and we welcome the government's intention to open up a route around the coast of England," commented Jo Burgon, head of access at the National Trust.
The bill also attempts to sort out the spatial planning issue, which currently sees areas vital for wildlife rubbing up against zones where oil and gas exploration is permitted.
The best example currently is in the Moray Firth, home to a population of bottlenose dolphins that conservationists fear are at risk from exploration activities planned in the area.
Recently the Department for Business, Enterprise and Regulatory Reform (Berr) issued its annual invitation for companies to bid for oil and gas exploration permits.
More of the sea floor than ever before is available, and some observers argue it would be sensible for the government to sort out which areas it wants to protect before advertising exploration licences.
There are questions over how much of the new powers set up in the bill will lie in Westminster, and how much with the devolved administrations.
Conservation groups say all the various authorities need to work together to ensure the whole of the UK's seas and the life in them receive the same levels of protection.
The government has promised it will turn the draft bill into law by the end of this parliament.