Olivia claims that the island they are on is "100 miles off the coast of Zanzibar". Zanzibar is an archipelago about 20 miles off the coast of Tanzania, East Africa, so it doesn't have a coastline as such. However the main island in the group, Unguja, is also known informally as Zanzibar so a charitable way of interpreting her statement is that they are situated 100 miles from there.