Humpback whales and tanker in Stellwagen Bank National Marine Sanctuary in Massachusetts Bay. Green Fire Productions/Flickr hide caption

toggle caption Green Fire Productions/Flickr

Helicopter belonging to the Netherlands participates in NATO's Dynamic Mongoose anti-submarine exercise in the North Sea, off the coast of Norway, on May 4, 2015. MARIT HOMMEDAL/AFP/Getty Images hide caption

toggle caption MARIT HOMMEDAL/AFP/Getty Images

NPR thanks our sponsors

Become an NPR sponsor