Hundreds of people have gathered in kayaks and small boats for a protest in the north-western US port city of Seattle against oil drilling in the Arctic by the Shell energy giant.
Paddle in Seattle is being held by activists who say the firm's drilling will damage the environment.
It comes after the first of Shell's two massive oil rigs arrived at the port.
The firm wants to move them in the summer to explore for oil off Alaska's northern coast.
Earlier this week, Shell won conditional approval from the US Department of Interior for oil exploration in the Arctic.
The Anglo-Dutch company still must obtain permits from the federal government and the state of Alaska to begin drilling.
'The only safe place'
The flotilla of kayaks, canoes, sailboats and paddle boats gathered near the 400ft (122m) tall Polar Pioneer drilling rig.
A solar-powered barge - The People's Platform - was also expected to join the protesters.
"This weekend is another opportunity for the people to demand that their voices be heard," Alli Harvey, Alaska representative for the Sierra Club's Our Wild America campaign, was quoted as saying by the Associated Press news agency.
"Science is as clear as day when it comes to drilling in the Arctic - the only safe place for these dirty fuels is in the ground.''
Demonstrators are also gathering on land to support the flotilla.
The port's Terminal 5 has been at the centre of a stand-off between environmentalists and the city authorities after a decision earlier this year to allow Shell use the terminal as a home base for the company's vessels and oil rigs during the winter months.
Shell stopped Arctic exploration more than two years ago after problems including an oil rig fire and safety failures.
The company has spent about $6bn (£3.85bn) on exploration in the Arctic - a region estimated to have about 20% of the world's undiscovered oil and gas.