Residents near the western coast of Washington have observed the 237-foot Greenpeace vessel Esperanza in area waters.
Joe Smyth, a Greenpeace spokesman, told regional newspaper Kitsap Sun that scientists and activists planned to deploy submersibles to monitor plans by Shell to drill in the arctic waters off the Alaskan coast.
"The crews will be using submarines to document the steep floor and the marine life along with various attributes of the Chukchi Sea," he said. "That will be part of a couple-month-long expedition we're undertaking to document the potential impacts of an oil spill in the Arctic and what Shell is doing up there."
A U.S. federal court in Alaska issued an injunction that would keep activists from Greenpeace away from Shell operations.
Shell aims to begin work this summer. Its 450-page response plan in the event of a spill was approved by the U.S. Interior Department's Bureau of Safety and Environmental Enforcement.