Why is it impossible for ships to sail all the way from Africa's interior to he sea?

It is impossible for ships to sail all the way from Africa's interior to the sea primarily due to the continent's geography, which features numerous rivers that are not navigable for large vessels. Many rivers have rapids, waterfalls, and changing water levels that hinder navigation. Additionally, the vast distances and the presence of land barriers, such as mountains and plateaus, further complicate direct access to the ocean. This limits maritime trade routes and necessitates the use of overland transport for goods moving from the interior to coastal ports.