The seabed is to be leased from the Queen to restore a kelp forest in a UK first.
Two West Sussex councils are in negotiations with the Crown Estate, hoping to bring back a historic carbon-storing kelp forest which once stretched from Selsey Bill to Shoreham.
The 100-mile undersea "forest" once provided a habitat for marine life including seahorses and lobster, as well as storing vast quantities of carbon, but 95 per cent of it has been lost since the late 1980s.
Neighbouring Adur and Worthing councils are hoping to enter into a "natural capital seabed lease" of the land, the first time any council has done this on the Crown’s seabed.
They say restoration could capture carbon emissions equivalent to 66 million miles driven in a family diesel car or those of 7,235 homes.
This lease would likely cover just the two councils’ coasts but they eventually hope to create a Sussex Bay Marine Park along the coast of the whole county to protect marine life and restore the estuary habitat for wildlife.
The project could also turn the spot into a destination for eco-tourism, the councils said.
The sea off Sussex was once home to a vast historic kelp forest, a haven for marine life stretching across 172 square kilometres, but 90 per cent of it has been lost in recent decades
The restoration of the kelp forest could also bring in funds, with companies and public bodies keen to invest in carbon capture projects to meet net zero targets.
Kelp forests are important habitats which can also improve water quality and mitigate coastal erosion by reducing the force of the waves.
They have been damaged by fishing methods which involve dragging nets along the seabed. In March trawling was banned in an area covering more than 100 square miles in an effort to help the kelp recover.
Angus Dunn, deputy leader of Adur District Council, said a regenerated kelp forest could be "absolutely massive" for the environment.
"The majority of the kelp forest went in ’87 in the great storm, which washed most of it up onto the beach.
"That, with a change in fishing methods, meant that the kelp wasn’t able to regenerate and so it is pretty bare out there.
"We’d like to regrow that. The benefits of the kelp forest are huge – not only does it protect the coastline, it provides a habitat for spawning fish and growing fish, and of course the carbon.
"Its ability to store carbon dioxide is huge, apparently 20 times greater per acre than a forest," he said.
Councillor Edward Crouch, Worthing Borough Council’s executive member for digital and environmental services, said: “This is a potential game-changing project which would help us cut carbon emissions, restore beautiful marine and estuarine habitats and perhaps even to create Sussex Bay as a destination for a whole host of sustainable marine activities.
“I am proud that this council is part of this project to become the first in the UK to lease the seabed from the Crown for this important environmental project. It shows that we have sustainability at the heart of everything we do.”
Councillor Emma Evans, Adur District Council’s executive member for the environment, said: “We have a bold vision and that is to see the waters off our coast and our estuaries teeming with marine life again, growing kelp that will capture tonnes of climate-warming carbon and signal that this area is serious about wanting to restore natural beauty while helping the environment.”
The Queen owns the seabed around the UK to a distance of 12 nautical miles away from the average low water point.
The Crown estate has previously leased offshore areas to wind farm projects and also granted seabed rights for the testing and demonstration of wave and tide-powered energy.