SEATTLE — One of two protesters who affixed themselves to an Arctic oil-drilling support ship parked north of Seattle left the vessel Sunday, but the other remained suspended from its anchor chain in an effort to draw attention to climate change and the risks an oil spill could pose in the remote waters off northwestern Alaska.

Protester Matt Fuller requested help getting down from the Arctic Challenger in Bellingham Bay about 4:30 a.m. Sunday, and the Coast Guard said it obliged.

The Arctic Challenger is part of a fleet Royal Dutch Shell expects to use to conduct exploratory drilling in the Chukchi Sea off northwestern Alaska this summer — plans that have drawn large protests in Seattle, where a massive, floating drill rig is being prepared for the excursion.

A student activist identified as Chiara D’Angelo suspended herself from the Arctic Challenger’s anchor chain on Friday night, and Fuller joined her early Saturday. In a telephone interview Sunday, Fuller, 37, said D’Angelo remained hanging from the anchor chain in a hammock.

Fuller called Shell’s plans “an affront to our planet and to our society and especially to the indigenous populations up in Alaska who rely on the fish for their subsistence and economic wellbeing.” He said he was motivated to protest by frustration with the administration of President Barack Obama, which has given a tentative green light to the project after finding that Shell had developed strong safeguards to protect against an oil spill.

Fuller said he didn’t have a hammock to rest in, but only a climbing harness and a less-than-stable piece of wood jammed into the anchor chain.

“It’s extraordinarily uncomfortable, sitting and standing on a 2-by-4 attached to a cold, giant anchor chain,” he said.

The Coast Guard brought Fuller to Coast Guard Station Bellingham, where he was met by medical staff and local police. He was found to be in good condition, and he was not arrested.

The Coast Guard said it has cited four owners or operators of protest vessels for violation of a 100-yard safety zone around the Arctic Challenger, and it blocked the voyages of two vessels determined to not have had the required safety gear. The agency also detained a small inflatable raft due to lack of proof of ownership.

“The Coast Guard has a duty to promote the safety of life at sea, which includes the encouragement of safe navigation in our ports and waterways by all waterway users,” Lt. Cmdr. Justin Noggle, chief of enforcement at Coast Guard Sector Puget Sound, said in a news release Sunday. “The Coast Guard respects the First Amendment rights of people to safely and lawfully assemble on the water. To that end, we will enforce those laws and regulations necessary to ensure the safety of the maritime public.”

The Arctic Challenger is a converted barge that is designed to launch containment equipment in the event of a spill. Protesters have questioned its ability to be effective in the harsh Arctic climate. A Shell spokesman did not immediately return an email seeking comment Sunday.

Obama said this month that he is committed to reducing carbon emissions. But he says consumers will still need fossil fuels during a transition to other energy sources, and he would rather rely on oil and gas extracted in the U.S. under federal regulations than from foreign sources.

Earlier this month, hundreds of activists in kayaks swarmed Elliott Bay in Seattle to protest Shell’s plans.