PORTLAND, Ore. - Protestors rappelled off a bridge and formed a kayak flotilla in Portland, Oregon, on Wednesday hoping to delay Royal Dutch Shell’s Arctic oil exploration this summer by blocking the return of a ship to Alaska that holds emergency equipment. Greenpeace said 13 protesters lowered themselves from the St. John’s bridge in the early morning and 13 others on the traffic level of the bridge were assisting them. “Depending on the weather they can stay there for three to five days,” said Cassady Sharp, a spokeswoman for Greenpeace, which says Arctic drilling could be damaging to populations of whales, polar bears and walrus if there is an oil spill. The danglers have food and water and plan to sleep in hammocks suspended over the Willamette River, which provides shipping access to the Pacific Ocean from Portland. Several activists also assembled in kayaks and small boats on the river below the bridge, holding a large #ShellNo sign, local broadcaster KOIN reported. No arrests had been made and the bridge was still open to traffic, police spokesman Pete Simpson said. The Fennica, an icebreaker Shell is leasing, was set to begin its journey back to Alaska on Wednesday morning, the protesters said, citing shipping charts. Its departure schedule has yet to be determined, boat repair facility Vigor said. The Fennica had returned to Portland in recent days for repairs to a three foot (1 meter) gash it suffered in Alaska earlier this month. The ship holds a capping stack, a piece of equipment that would help plug a oil well, should one blow out. Until the Fennica returns to the Chukchi Sea off northern Alaska with this emergency equipment, Shell is not allowed to drill into the oil bearing zone, the Interior Department said last week in issuing the final permits for exploration. Any delays could be costly as the exploration season only lasts until about October, when sea ice returns. President Barack Obama has tried to strike a balance in the Arctic by expanding protected areas of Alaska’s Arctic National Wildlife Refuge this spring. But at the same time his Interior Department is allowing Shell to return to drilling leases the company obtained when George W. Bush was president. “The Fennica will begin its return journey to Alaska once we’ve completed the final preparations,” Shell spokesman Curtis Smith said. Shell hopes to return to the Arctic for the first time since 2012, when it experienced a series of mishaps including the grounding of an oil rig.