Over the course of 400 years, the transatlantic slave trade trafficked in 12 million people, two million of whom died at sea. Bringing new perspective, the group Diving with a Purpose (DWP) explores sunken slave ships worldwide, and as they uncover manilla bracelets, shackles, and other possessions, they bring the stories of lost lives back to the surface. A companion to the BBC documentary series featuring Samuel L. Jackson, this informal history of the slave trade shows that it touched nearly every nation on earth.