Greenpeace flies the A.E. Bates thermal airship over Walmart's world headquarters one day before the company's annual shareholders meeting with messages reading "Save Oceans Protect Workers" and "Walmart Cleanup Needed in the Tuna Aisle." Greenpeace is asking the world's largest retailer to stop buying tuna from Thai Union Group to stop ocean destruction and human rights abuses of workers in the global tuna trade.