Navigable describes water that's deep and wide enough for boats or ships to travel through safely. A navigable river has sufficient depth that vessels won't scrape the bottom, and enough width that they can steer without running into banks or obstacles. The Mississippi River is navigable for hundreds of miles, which is why it became such an important trade route for American commerce.

For a waterway to be navigable, it needs reliable depth throughout the year, a current that isn't too dangerous, and channels wide enough for the boats using it. A shallow creek might be fun for wading, but it's not navigable. A deep but narrow canyon river with rapids isn't navigable either, at least not safely.

Throughout history, navigable waterways shaped where cities grew and how economies developed. Ports on navigable rivers or harbors became centers of trade and culture because ships could reach them reliably. Even today, enormous cargo ships follow navigable channels, sometimes dredged deeper by engineers to keep them suitable for modern vessels.