On a starless night in March, a group of Afghans, Chinese, Venezuelan, and Ecuadorian migrants waded toward a clandestine boat in Colombia, headed for the Darién Gap. A haze blurred a full moon. A boat captain barked at them to turn off their phones, so they could travel undetected by the police. The motor roared, and the 54 Afghans sped up the coast, crying, vomiting and praying. Many had never seen the ocean before. Capurgana, Colombia.