Thirteen Greenpeace campaigners have been arrested after a protest on board one of the world's largest freighters, carrying genetically-modified maize.
Protesters stopped the ship moving at high tide
Police officers were flown onto the Etoile, moored off Rhoose in Wales, on Monday to negotiate with protesters who had chained themselves to the vessel.
The 13 were arrested on charges relating to causing a public nuisance.
The Etoile has now reached Royal Portbury Dock near Bristol, its destination before being boarded.
Acting Assistant Chief Constable Brian Greaves from South Wales Police said the protest ended safely after negotiations between the ship owners and the protesters.
The protest began on Sunday night, when the campaigners forced their way aboard the 125,000 tonne boat, one of the world's largest freighters, minutes before it was due to dock.
The campaigners stopped a pilot from boarding the vessel, ensuring the ship missed three high tides, the only time such vessels can safely enter harbour.
Two campaigners had been suspended on ropes above the propeller to prevent it from being moved while three others were positioned on the mast.
But Greenpeace members were claiming a victory on Monday night as they successfully stopped the ship which had set sail from Louisiana, USA, from moving at high tide.
Spokesman Ben Stewart said: "It has been a success in that we have forced the ship to stay at sea for 36 hours - it has still not docked."
Earlier in the day, one of the protesters on board, Ben Ayliffe, said: "We're going to stay here for as long as we possibly can. We are well set... we're very committed to making sure this ship turns round with its cargo of GM crops - goes back to the USA."
Some protesters tied or chained themselves to the vessel
Greenpeace claims that supermarkets which claim to be GM free, are actually supporting huge imports of GM crops by selling milk from cows fed on GM products.
Supermarkets have responded through the Retail Federation and say that Greenpeace is creating unnecessary food fears through misleading claims.
The Foods Standards Agency, they added, had categorically stated that milk from animals fed on GM crops did not contain any GM material.