It is April, and large groups of blacktip and tiger sharks are gathering off the South African Coast. They are waiting for the onset of one of nature’s most spectacular mass migrations: the annual sardine run. Like the cold ocean current that gives rise to the extraordinary numbers of African pilchards and their predators during the Sardine Run, the frigid Benguela current that runs northwards along the arid coastline of Namibia also supports a remarkable diversity of life.