A 50-mile stretch of the River Waveney is now accessible to canoeists after nearly 400 landowners cleared up banks.
Biodiversity minister Barry Gardiner canoeing on River Waveney
The project along the main boundary between Norfolk and Suffolk was backed by the Environment Agency.
Minister for Biodiversity Barry Gardiner came to Bungay in Suffolk to inaugurate the scheme.
He said: "We asked landowners if they would undertake an access agreement so that canoeists and boaters could use the river."
The Environment Agency aims to encourage people to pursue healthy activities like canoeing and other water sports.
"Access agreements set the watermark for future voluntary schemes across the country," the agency's acting chief executive, Dr Paul Leinster, said.
"The Environment Agency has a statutory duty to promote the use of water and watersides for recreation, at the same time balancing the needs of the competing water users and the environment.
"The popularity of canoeing is increasing and if more water is made available, more people will be encouraged to take part."