The ocean looks like peace from afar and truth up close, they say. But beneath the waves, the map of the world’s oceans is far less settled than it looks. Today, dozens of sea borders remain unresolved. Like so many conflicts, they owe their origins to complicated questions of where one country’s territory ends, and another’s begins. Many involve overlapping claims to areas rich in resources; and a disproportionate number concern the waters of the Global South. Africa’s coastline is a stark...