(CNN) -- Environmental activists with Greenpeace on Sunday swam in front of a Chevron oil drilling ship in the group's latest effort to prevent the giant vessel from reaching a drill site in the North Sea.
Activists on board the Greenpeace ship Esperanza reached the drill ship's location Sunday afternoon by inflatable speedboat. Four wetsuit-clad activists entered the frigid water, forcing the Stena Carron to change course and hold its position 100 miles north of the Shetland Islands. The activists carried a bright orange buoy with a flag attached reading, "go beyond oil."
"That oil drill ship is the size of a skyscraper on its side and as it cut through the water towards us I felt really scared," said Ben Stewart, one of the swimmers. "It's like nothing I've ever done, but we are determined to stop it reaching its deepwater drilling site."
Greenpeace said in a news release Sunday that it intends to continue to send swimmers into the water as well as kayakers over the next 48 hours in hopes of turning the ship back.
Chevron appealed to the group Sunday "to end its new protest at the Stena Carron while it is going about its lawful business north of Shetland."
"This latest act is extremely dangerous and once again demonstrates that Greenpeace is willing to put its volunteers at risk by entering the path of the Stena Carron while the vessel is in transit," a statement from the oil company said. "Chevron is concerned for the safety of those involved and, while we acknowledge and respect the right of Greenpeace to express its views by peaceful and lawful action, we condemn activities that put people at risk."
The group has been disrupting the ship since Wednesday, when activists attached a "survival pod" to the Stena Carron's anchor. The pod contained enough food, fuel and other supplies to sustain its occupants for a month, Greenpeace said.
But the activists were forced to detach the pod Saturday after Chevron and the Stena Carron were granted an injunction a day earlier against the demonstration by a Scottish court. Under the injunction, the activists were ordered to cease their demonstration or incur major daily fines.
"We hoped that Greenpeace would continue to respect the interdict granted by the court, which prohibits the activists from returning to the Stena Carron, but this gesture shows no regard for the law and for the safety of all involved," Chevron's statement said.
Greenpeace is campaigning for a ban on new deepwater drilling in the wake of the BP oil disaster in the Gulf of Mexico, which began when a rig exploded and sank in April.
"We need to go beyond oil, we need our politicians to stop ships like this from threatening our pristine coastlines and the global climate," Stewart said. "It shouldn't be down to people bobbing in the water in front of ships to stop the insane rush for the last drops of oil in ever more dangerous and difficult-to-reach places."
Chevron defended its safety practices in its statement Sunday, saying "We are confident our operations are safe and we can drill deep water wells in the Atlantic margin safely and without environmental harm."
CNN's Sarah Aarthun contributed to this report.