Campaigners will protest about the proposed power station in August
Environmental campaigners plan to launch a flotilla of craft on the River Medway during a week-long demonstration at Kingsnorth power station in Kent.
The organisers of the Climate Camp event in August said the craft would surround the plant to help their attempt to shut the station.
They want to bring it to a standstill to protest about plans to build a new coal-fired plant near Hoo.
Kent Police said action would be taken against anyone breaking the law.
Organisers said they expected up to 2,000 people to take part in the Camp for Climate Action, which will be held at E.ON's Kingsnorth site in Kent from 3 to 12 August.
Sarah Jenkins, who is one of those co-ordinating the armada, said: "Once on the river we will swim towards Kingsnorth like a giant shoal of disobedient fish, all with one simple and achievable aim in mind: shutting down the climate criminal."
Two public meetings organised by Kent Police have been held to inform locals about their policing plans for the event.
Ch Insp Des Keers said the force intended to police a lawful and peaceful protest, but it would not hesitate to bring offenders to justice.
E.ON said the new power station would be 20% cleaner than the one it replaced but supported the campaigners right to hold a peaceful protest on public land.
The first Camp for Climate Action, held at Heathrow Airport in August 2007, was attended by more than 1,000 protesters.
It required up to 1,800 police on busy days, with policing costs of more than £7m, according to Scotland Yard.
In 2007 a group of Greenpeace activists broke into the power station, near Hoo, before abseiling down the stack.