Early Wednesday morning, activists created a human barricade across the Willamette River in Portland, Ore., in an attempt to block the MSV Fennica, an icebreaking vessel, from reaching Royal Dutch Shell’s Arctic drilling fleet in Alaska. Thirteen climbers associated with Greenpeace rappelled from the St. John’s Bridge while over 50 kayakers lined the channel below.

The action is the latest in a series of paddler protests against Shell’s plans to drill in the Chukchi Sea. In May, over 500 kayakers and canoeists gathered outside of Seattle to draw attention to a Shell drilling rig which was docked outside the city. And in June, 13 activists including Seattle Councilman Mike O'Brien were detained after attempting to block the rig from leaving port.

Protesters are concerned tapping new oil reserves could exacerbate climate change and are skeptical of Shell’s ability to safely drill in the Arctic, despite the company’s claims to the contrary. Critics have accused the kayaktivists of hypocrisy since most kayaks and canoes are made with petroleum.

The icebreaker was scheduled to leave Portland on Wednesday, but its departure appears to have been delayed. Activists told the Seattle Times they have enough supplies to remain dangling from the bridge for multiple days and plan to resupply if necessary. Shell cannot begin drilling until the icebreaker is on site.

–Watch a VIDEO from the May kayaktivist protests, and read an op-ed about the actions.