Narrow boats and other vessels have been cruising along east London waterways in a floating protest against the London 2012 Olympic bid.
An artist's impression of the proposed Olympic Park in east London
River users say planned development along the banks of the River Lea will result in the loss of common land and destroy recreational activities.
The protest comes before a visit by the International Olympic Committee (IOC).
London 2012 said there were huge benefits and the vast majority of east Londoners backed the bid.
Protesters, who took to the water on Saturday, also say building on the river will disrupt flood relief systems, threaten wildlife habitats and lead to more than 500 mature trees being felled.
Boat owner Ashley Gunnell said: "Hundreds of people use the river and its banks - whether it's for dog-walking and cycling or fishing and canoeing.
"The planners of the bid don't know this area and they have assumed it's all derelict and ripe for their so-called regeneration.
"The area does need investment, but for the benefit of local people, not corporate sponsors."
A spokeswoman for London 2012 told BBC News the bid was supported by the London Wildlife Trust and British Waterways, and the games would bring 26% more open space to the area.
"This area has been neglected for a long time. The area's going to be at the heart of the bid."
She said the rivers, which are currently polluted, would be cleaned up and access to the river would be improved by land bridges.