( CNN ) -- Greenpeace activists who have interfered with the launch of a Chevron oil drilling ship in the North Sea say that they have enough fuel and supplies to last several weeks . Activists on board the Greenpeace ship Esperanza attached a bright yellow `` survival pod '' to the giant ship 's anchor on Wednesday , effectively keeping it from going to sea . The drill ship Stena Carron , operated under contract by oil giant Chevron , is now holding off the Shetland Islands in the North Sea . Two members of the crew shimmied up the chains , spending Tuesday night hanging above the waves in a small tent . They then secured the survival pod , which is now occupied by two new activists . Inside the ball , there 's enough food , fuel and water and even a small toilet to sustain the occupants for up to a month , Greenpeace says . Ben Stewart , leader of the operation , told CNN via satellite phone from the scene that a storm is approaching , but the crew and the activists are safe . The bright yellow `` survival pod '' attached to the giant ship 's anchor effectively keeps it from going to sea . The 2-meter diameter pod is hanging from the chain , preventing it from being raised high enough for the 748-foot ( 228-meter ) ship to safely embark . Stewart says that they will stay as long as possible , adding `` every day they are held back is a day that we can avoid the chance of another Gulf of Mexico-style environmental disaster in the North Sea . '' The group hopes to pressure Chevron and European Union environmental ministers gathering this week in Norway to support a deepwater drilling moratorium in the North Sea . Chevron says it has been in contact with the activists and stressed the need for safety . `` We fully acknowledge and respect the right of Greenpeace or anyone else to express their views by peaceful and lawful action . '' Chevron said in a press release . `` However , we are deeply concerned about activities that put people at risk . '' Greenpeace says it has assured the captain of the Stena Carron it will not interfere with the second anchor so the ship will not float into danger . It 's the second such boarding action by the Greenpeace team in recent weeks . They boarded an oil drilling rig operated by British company Cairn Energy in Arctic waters off Greenland in August .
Activists have enough fuel and supplies to last several weeks , Greenpeace says . Two people occupy `` survival pod '' attached to ship 's anchor , preventing departure . Group hopes to pressure Chevron , EU to support North Sea drilling moratorium .