SEATTLE — Six Greenpeace activists opposed to offshore drilling in the Arctic have abandoned a Seattle-bound drill rig they boarded in the Pacific Ocean six days ago, the organization said Saturday.

Rough seas prompted the decision, Greenpeace said in an email. The protesters rappelled off the rig and got into inflatable boats before returning to a Greenpeace ship stationed nearby.

The six climbed on the Polar Pioneer, a 400-foot rig owned by Transocean Ltd., about 750 miles northwest of Hawaii on Monday. A heavy-lift vessel called the Blue Marlin is transporting the rig to Seattle for staging.

Royal Dutch Shell, which leased the rig, hopes to use it for exploratory drilling during the summer open-water season in the Chukchi Sea off Alaska’s northwest coast if it can obtain all necessary permits.

Meanwhile, U.S. District Court Judge Sharon Gleason in Anchorage, Alaska, on Saturday granted Shell a restraining order against the protesters. The order, issued Saturday, prohibits Greenpeace activists from entering a safety zone around the rig and the Blue Marlin.

Shell spokeswoman Kelly op de Weegh said the company is pleased with the order. “These tactics are not peaceful protests. They jeopardize the safety of the people working on board and the protesters themselves, especially aboard a moving vessel at sea,” she said in an email.

Reacting to the decision, Greenpeace USA spokesman Travis Nichols said his group “maintains its position that this is not the proper venue for Shell’s complaint and will be prepared for further legal arguments at the preliminary injunction hearing on April 28.”

Conservationists bitterly oppose Arctic offshore drilling. They say oil companies have not demonstrated that they can clean up a major spill in ocean water choked with ice, and they argue that the drilling takes place far from infrastructure such as Coast Guard bases, deep-water ports, major airports and other resources that could be of use in a spill.

“We’re coming down for safety—something we value,” one of the protesters, Zoe Buckley Lennox, wrote on Twitter. “Shell’s reckless plans speak volumes about their disregard for it.”

Shell has also asked the U.S. court for an injunction against further Greenpeace actions on Shell ships bound for or already in the Arctic. The court issued a similar order in 2012, the last time Shell conducted exploratory drilling in the Arctic.

“Greenpeace USA has now resumed its reckless behavior towards Shell,” the company wrote in a court filing Wednesday. “As soon as Shell announced its intention to return to the Arctic for the summer of 2015, Greenpeace USA immediately reinitiated its campaign to stop Shell.”

The judge plans to hear arguments April 28.

The company Royal Dutch Shell hired that year to drill on petroleum leases in the Chukchi Sea — Sugar Land, Texas-based Noble Drilling U.S. LLC — agreed to pay $12.2 million in December after pleading guilty to eight felony environmental and maritime crimes on board the Noble Discoverer. That rig is the second one Shell intends to use this year if it obtains the necessary permits.