Greenpeace activists on Tuesday stepped up protests against sending a decommissioned French aircraft carrier to India for scrapping.
An activist was camped aboard the 44-year-old Clemenceau, the environmental group said.
Earlier, three protesters jumped from small boats to Clemenceau, kept in the Mediterranean port of Toulon.
Two activists left the ship and joined four of their fellow campaigners, who were taken into French police custody.
They has earlier unfurled a banner that said: "Asbestos carrier: not here, nor elsewhere."
Greenpeace said it organised the protests to highlight the carcinogenic danger posed by the vessel and to urge the French government to remove the asbestos instead of sending the carrier to India.
The French government intends to send the Clemenceau to India to be broken down into thousands of tonnes of scrap metal.