Greenpeace flew its thermal airship and drove a mobile billboard truck around Walmart's annual general meeting this week to highlight the company's failure to address ocean destruction and potential human rights abuses in its tuna supply chain. The airship featured banners that read, "Walmart: Clean up needed in the tuna aisle" and "Save oceans. Protect workers." The mobile billboard truck broadcasted graphics about Walmart's destructive Great Value canned tuna, which is supplied by Thai Union -- the largest tuna company in the world and owner of Chicken of the Sea.