How can two coastlines be separated by an ocean and have matching shapes?

Two coastlines separated by an ocean can have matching shapes due to continental drift. As continents slowly move across the Earth's surface over geologic time, they can split apart, resulting in the formation of ocean basins. However, the edges of these continents, now coastlines, may retain similar or complementary shapes due to their shared geologic history and the processes that shaped their landforms before they separated.